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Brown CD, Wang Y, Namazi M, Harris GI, Uysal MT, Harris JGE. Superfluid Helium Drops Levitated in High Vacuum. PHYSICAL REVIEW LETTERS 2023; 130:216001. [PMID: 37295082 DOI: 10.1103/physrevlett.130.216001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 01/19/2023] [Accepted: 04/04/2023] [Indexed: 06/12/2023]
Abstract
We demonstrate the trapping of millimeter-scale superfluid helium drops in high vacuum. The drops are sufficiently isolated that they remain trapped indefinitely, cool by evaporation to 330 mK, and exhibit mechanical damping that is limited by internal processes. The drops are also shown to host optical whispering gallery modes. The approach described here combines the advantages of multiple techniques, and should offer access to new experimental regimes of cold chemistry, superfluid physics, and optomechanics.
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Affiliation(s)
- C D Brown
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Yale Quantum Institute, Yale University, New Haven, Connecticut 06520, USA
| | - Y Wang
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
| | - M Namazi
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Yale Quantum Institute, Yale University, New Haven, Connecticut 06520, USA
| | - G I Harris
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- AARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - M T Uysal
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - J G E Harris
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Yale Quantum Institute, Yale University, New Haven, Connecticut 06520, USA
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
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2
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von Haeften K, Laarmann T, Wabnitz H, Möller T. Relaxation dynamics of 3He and 4He clusters and droplets studied using near infrared and visible fluorescence excitation spectroscopy. Phys Chem Chem Phys 2023; 25:1863-1880. [PMID: 36541224 DOI: 10.1039/d2cp04594j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The relaxation dynamics of electronically excited 3He and 4He clusters and droplets is investigated using time-correlated near-infrared and visible (NIR/VIS) fluorescence excitation spectroscopy. A rich data set spanning a wide range of cluster and droplet sizes is produced. The spectral features broadly follow the vacuum ultraviolet excitation (VUV) spectra. However, when the NIR/VIS spectra are normalised to the VUV fluorescence, regions with distinctly different cluster size and isotope dependence are identified, enabling deeper insight into the relaxation mechanism. Particle density, location of atomic-like states and their principal quantum number, n, are found to play an important role in the relaxation. For states with n = 3 and higher, only energy within the surface region is transferred to excited atoms which are subsequently ejected from the surface and fluoresce in vacuum. For states with n = 2, energy from the entire region within clusters and droplets is transferred to the surface, leading to the ejection of excited atoms and excimers. Here, the energy is transferred by excitation hopping, which competes with radiative and non-radiative decay, making ejection and NIR/VIS fluorescence inefficient in increasingly larger droplets.
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3
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Gallegos MV, Reimers WG, Luna CR, Damonte LC, Sambeth J, Marchetti J, Juan A. Theoretical analysis of Polyethylene terephthalate (PET) adsorption on Co and Mn-doped ZnO (000-1). MOLECULAR CATALYSIS 2022. [DOI: 10.1016/j.mcat.2022.112688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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4
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Tanyag RMP, Bacellar C, Pang W, Bernando C, Gomez LF, Jones CF, Ferguson KR, Kwok J, Anielski D, Belkacem A, Boll R, Bozek J, Carron S, Chen G, Delmas T, Englert L, Epp SW, Erk B, Foucar L, Hartmann R, Hexemer A, Huth M, Leone SR, Ma JH, Marchesini S, Neumark DM, Poon BK, Prell J, Rolles D, Rudek B, Rudenko A, Seifrid M, Swiggers M, Ullrich J, Weise F, Zwart P, Bostedt C, Gessner O, Vilesov AF. Sizes of pure and doped helium droplets from single shot x-ray imaging. J Chem Phys 2022; 156:041102. [PMID: 35105059 DOI: 10.1063/5.0080342] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Advancements in x-ray free-electron lasers on producing ultrashort, ultrabright, and coherent x-ray pulses enable single-shot imaging of fragile nanostructures, such as superfluid helium droplets. This imaging technique gives unique access to the sizes and shapes of individual droplets. In the past, such droplet characteristics have only been indirectly inferred by ensemble averaging techniques. Here, we report on the size distributions of both pure and doped droplets collected from single-shot x-ray imaging and produced from the free-jet expansion of helium through a 5 μm diameter nozzle at 20 bars and nozzle temperatures ranging from 4.2 to 9 K. This work extends the measurement of large helium nanodroplets containing 109-1011 atoms, which are shown to follow an exponential size distribution. Additionally, we demonstrate that the size distributions of the doped droplets follow those of the pure droplets at the same stagnation condition but with smaller average sizes.
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Affiliation(s)
- Rico Mayro P Tanyag
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Camila Bacellar
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Weiwu Pang
- Department of Computer Science, University of Southern California, Los Angeles, California 90089, USA
| | - Charles Bernando
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, USA
| | - Luis F Gomez
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Curtis F Jones
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Ken R Ferguson
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Justin Kwok
- Department of Chemical Engineering and Material Science, University of Southern California, Los Angeles, California 90089, USA
| | - Denis Anielski
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Ali Belkacem
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Rebecca Boll
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - John Bozek
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Sebastian Carron
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Gang Chen
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Tjark Delmas
- Center for Free-Electron Laser Science (CFEL), Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany
| | - Lars Englert
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85741 Garching, Germany
| | - Sascha W Epp
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Benjamin Erk
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Lutz Foucar
- Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany
| | | | - Alexander Hexemer
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Martin Huth
- PNSensor GmbH, Otto-Hahn-Ring 6, 81739 München, Germany
| | - Stephen R Leone
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jonathan H Ma
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Stefano Marchesini
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Daniel M Neumark
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Billy K Poon
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - James Prell
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Daniel Rolles
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Benedikt Rudek
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Artem Rudenko
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Martin Seifrid
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Michele Swiggers
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Joachim Ullrich
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Fabian Weise
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Petrus Zwart
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Christoph Bostedt
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Oliver Gessner
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Andrey F Vilesov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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5
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Abstract
A beam of size-selected charged helium droplets was crossed with an electron beam, and the ion efficiency curves for the product droplets in all different charge states were recorded. We estimate that the selected helium droplets on their passage through the electron beam are hit by several hundred electrons which can interact with the individual He atoms of the droplets. Reaction channels corresponding to the removal or capture of up to eight electrons were identified, and in all cases, inelastic scattering and the formation of metastable helium played a significant role.
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7
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González-Lezana T, Echt O, Gatchell M, Bartolomei M, Campos-Martínez J, Scheier P. Solvation of ions in helium. INT REV PHYS CHEM 2020. [DOI: 10.1080/0144235x.2020.1794585] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Tomás González-Lezana
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas IFF-CSIC, Madrid, Spain
| | - Olof Echt
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
- Department of Physics, University of New Hampshire, Durham, NH, USA
| | - Michael Gatchell
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
- Department of Physics, Stockholm University, Stockholm, Sweden
| | - Massimiliano Bartolomei
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas IFF-CSIC, Madrid, Spain
| | - José Campos-Martínez
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas IFF-CSIC, Madrid, Spain
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
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8
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Tanyag RMP, Feinberg AJ, O’Connell SMO, Vilesov AF. Disintegration of diminutive liquid helium jets in vacuum. J Chem Phys 2020; 152:234306. [DOI: 10.1063/5.0004503] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- Rico Mayro P. Tanyag
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Alexandra J. Feinberg
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Sean M. O. O’Connell
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Andrey F. Vilesov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, USA
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9
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Laimer F, Kranabetter L, Tiefenthaler L, Albertini S, Zappa F, Ellis AM, Gatchell M, Scheier P. Highly Charged Droplets of Superfluid Helium. PHYSICAL REVIEW LETTERS 2019; 123:165301. [PMID: 31702350 DOI: 10.1103/physrevlett.123.165301] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 08/26/2019] [Indexed: 05/18/2023]
Abstract
We report on the production and study of stable, highly charged droplets of superfluid helium. Using a novel experimental setup we produce neutral beams of liquid helium nanodroplets containing millions of atoms or more that can be ionized by electron impact, mass-per-charge selected, and ionized a second time before being analyzed. Droplets containing up to 55 net positive charges are identified and the appearance sizes of multiply charge droplets are determined as a function of the charge state. We show that the droplets are stable on the millisecond timescale of the experiment and decay through the loss of small charged clusters, not through symmetric Coulomb explosions.
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Affiliation(s)
- Felix Laimer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Lorenz Kranabetter
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Lukas Tiefenthaler
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Simon Albertini
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Fabio Zappa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
- Departamento de Física-ICE, Universidade Federal de Juiz de Fora, Campus Universitário, 36036-900, Juiz de Fora, MG, Brazil
| | - Andrew M Ellis
- Department of Chemistry, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
| | - Michael Gatchell
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
- Department of Physics, Stockholm University, 106 91 Stockholm, Sweden
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
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10
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Abstract
Free superfluid helium droplets constitute a versatile medium for a diverse range of experiments in physics and chemistry that extend from studies of the fundamental laws of superfluid motion to the synthesis of novel nanomaterials. In particular, the emergence of quantum vortices in rotating helium droplets is one of the most dramatic hallmarks of superfluidity and gives detailed access to the wave function describing the quantum liquid. This review provides an introduction to quantum vorticity in helium droplets, followed by a historical account of experiments on vortex visualization in bulk superfluid helium and a more detailed discussion of recent advances in the study of the rotational motion of isolated, nano- to micrometer-scale superfluid helium droplets. Ultrafast X-ray and extreme ultraviolet scattering techniques enabled by X-ray free-electron lasers and high-order harmonic generation in particular have facilitated the in situ detection of droplet shapes and the imaging of vortex structures inside individual, isolated droplets. New applications of helium droplets ranging from studies of quantum phase separations to mechanisms of low-temperature aggregation are discussed.
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Affiliation(s)
- Oliver Gessner
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Andrey F. Vilesov
- Department of Chemistry and Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, USA
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11
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de Aquino ABM, Leal LA, Carvalho-Silva VH, Gargano R, Ribeiro Junior LA, da Cunha WF. Krypton-methanol spectroscopic study: Assessment of the complexation dynamics and the role of the van der Waals interaction. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2018; 205:179-185. [PMID: 30015023 DOI: 10.1016/j.saa.2018.06.110] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 06/26/2018] [Accepted: 06/30/2018] [Indexed: 06/08/2023]
Abstract
The Kr-CH3OH (Krypton-Methanol) system has several technological applications, such as the determination of diffusivity coefficients, their use in the development of detectors and combustion techniques among others. We report an extensive theoretical study concerning the stability of such complex. A mix between molecular dynamics, electronic structure calculations and solution of the nuclear Schrodinger equation lead to investigation of spectroscopic constants, lifetime of the complex and its Quantum Theory Atom in Molecules (QTAIM) properties. The study of the Potential Energy Curves (PEC) suggested three configurations to be stable as their potential well were able to harbor 9 vibrational levels. Properties from the curves also allowed us to obtain the lifetime of the complex, whose values were >1 ps regardless of the conformation. Furthermore, topological investigations of the charge density profile of the complex, in the scope of QTAIM properties, show that van der Waals type interactions takes place between the noble gas and the methanol molecule. These features are in consonance to the experimental fact that this complex is stable.
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Affiliation(s)
- Amanda Bárbara Mendes de Aquino
- Anapolis Group of Theoretical and Structural Chemistry, Goias State University - Exact Science and Technology Campus, Anapolis 75001-970, Brazil
| | | | - Valter H Carvalho-Silva
- Anapolis Group of Theoretical and Structural Chemistry, Goias State University - Exact Science and Technology Campus, Anapolis 75001-970, Brazil
| | - Ricardo Gargano
- Institute of Physics, University of Brasilia, Brasilia 70910-900, Brazil
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12
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Ancilotto F, Barranco M, Coppens F, Eloranta J, Halberstadt N, Hernando A, Mateo D, Pi M. Density functional theory of doped superfluid liquid helium and nanodroplets. INT REV PHYS CHEM 2017. [DOI: 10.1080/0144235x.2017.1351672] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Francesco Ancilotto
- Dipartimento di Fisica e Astronomia ‘Galileo Galilei’ and CNISM, Università di Padova, Padova, Italy
- CNR-IOM Democritos, Trieste, Italy
| | - Manuel Barranco
- Facultat de Física, Departament FQA, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - François Coppens
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - Jussi Eloranta
- Department of Chemistry and Biochemistry, California State University at Northridge, Northridge, CA, USA
| | - Nadine Halberstadt
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - Alberto Hernando
- Social Thermodynamics Applied Research (SThAR), EPFL Innovation Park, Lausanne, Switzerland
| | - David Mateo
- Applied Complexity Group, Singapore University of Technology and Design, Singapore, Singapore
| | - Martí Pi
- Facultat de Física, Departament FQA, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
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13
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Farrokhpour H, Dehdashti Jahromi M. Absorption spectra of small helium Nano clusters (4He ; n= 2–29) and characterization of their low-lying excited states. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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14
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Thomas BJ, Harruff-Miller BA, Lewis WK. Note: A simple detection method for helium droplet spectroscopy experiments. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2017; 88:016101. [PMID: 28147675 DOI: 10.1063/1.4973775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Helium droplet methods are currently established as a premier experimental technique for the production and spectroscopic study of novel clusters and complexes. Unfortunately, some of the essential equipment required to perform the experiments, such as the detector used to monitor photon-induced depletion of the helium droplet beam, can be relatively large, complex, and expensive. Most often this detector is a quadrupole mass spectrometer (QMS). In this report, we describe the development and evaluation of an extremely simple, straightforward, small, and inexpensive droplet beam detector for use in helium droplet spectroscopy experiments and compare its performance to that of a QMS by recording the infrared spectra of helium droplets doped with either 13CO2 or CD4.
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Affiliation(s)
- Brandon J Thomas
- U.S. Food and Drug Administration, Division of Pharmaceutical Analysis, St. Louis, Missouri 63110, USA
| | - Barbara A Harruff-Miller
- Energy Technology and Materials Division, University of Dayton Research Institute, Dayton, Ohio 45469, USA
| | - William K Lewis
- U.S. Air Force Research Laboratory, Aerospace Systems Directorate, Wright-Patterson AFB, Ohio 45433, USA
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15
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Rodríguez-Cantano R, González-Lezana T, Villarreal P. Path integral Monte Carlo investigations on doped helium clusters. INT REV PHYS CHEM 2016. [DOI: 10.1080/0144235x.2015.1132595] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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16
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Lewis WK, Harruff-Miller BA, Leatherman P, Gord MA, Bunker CE. Helium droplet calorimetry of strongly bound species: carbon clusters from C₂ to C₁₂. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:094102. [PMID: 25273742 DOI: 10.1063/1.4895670] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Helium droplet beam methods are a versatile technique that can be used to assemble a wide variety of atomic and molecular clusters. In recent years, methods have been developed to utilize helium droplets as nano-calorimeters to measure the binding energies of weakly bound complexes assembled within the droplet. In the current investigation we extend the helium droplet calorimetry approach to the study of a very strongly bound system: carbon clusters which are bound by several eV per atom. We utilize laser heating of bulk carbon samples to dope the helium droplets with evaporated carbon species. Depending on the laser target, the vaporization plume is found to consist primarily of C3 alone or C2 and C3. These species are sequentially captured by the droplet and assembled into larger carbon clusters in a stepwise manner. The assembled C(n) clusters are detected via mass spectrometry of the doped droplets and the droplet sizes required to detect the various carbon clusters observed are used to estimate the reaction energies of the associated assembly pathways. The helium droplet data qualitatively reflect the trends in assembly energetics, but at first glance appear to yield energies that differ dramatically from theoretical values. Statistical modeling of the helium droplet calorimetry experiment reconciles the differences quantitatively. Our modeling also generates a calibration curve that relates the assembly/reaction energy and threshold mean droplet size over a range of energies from van der Waals interactions to chemical bonding, enabling helium droplet calorimetry methods to be applied quantitatively to a large number of systems.
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Affiliation(s)
- William K Lewis
- Air Force Research Laboratory, Aerospace Systems Directorate, Wright-Patterson Air Force Base, Ohio 45433, USA
| | - Barbara A Harruff-Miller
- Energy Technology & Materials Division, University of Dayton Research Institute, Dayton, Ohio 45469, USA
| | - Peter Leatherman
- Energy Technology & Materials Division, University of Dayton Research Institute, Dayton, Ohio 45469, USA
| | - Michael A Gord
- Energy Technology & Materials Division, University of Dayton Research Institute, Dayton, Ohio 45469, USA
| | - Christopher E Bunker
- Air Force Research Laboratory, Aerospace Systems Directorate, Wright-Patterson Air Force Base, Ohio 45433, USA
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17
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Mateo D, Eloranta J. Solvation of Intrinsic Positive Charge in Superfluid Helium. J Phys Chem A 2014; 118:6407-15. [DOI: 10.1021/jp501451y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- David Mateo
- Department
of Chemistry and Biochemistry, California State University at Northridge, 18111 Nordhoff Street, Northridge, California 91330, United States
| | - Jussi Eloranta
- Department
of Chemistry and Biochemistry, California State University at Northridge, 18111 Nordhoff Street, Northridge, California 91330, United States
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18
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Affiliation(s)
- J. Peter Toennies
- a Max-Planck-Institut für Dynamik und Selbstorganisation , Göttingen , Germany
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19
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Zhang C, Zhang Z, Huang C, Zhang Q, Chen Y. Helium Droplets: An Apparatus to Study Ultra Cold Chemistry. CHINESE J CHEM PHYS 2013. [DOI: 10.1063/1674-0068/26/03/270-276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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20
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Lewis WK, Harruff-Miller BA, Gord MA, Gord JR, Guliants EA, Bunker CE. A threshold-based approach to calorimetry in helium droplets: measurement of binding energies of water clusters. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:073109. [PMID: 22852673 DOI: 10.1063/1.4738664] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Helium droplet beam methods have emerged as a versatile technique that can be used to assemble a wide variety of atomic and molecular clusters. We have developed a method to measure the binding energies of clusters assembled in helium droplets by determining the minimum droplet sizes required to assemble and detect selected clusters in the spectrum of the doped droplet beam. The differences in the droplet sizes required between the various multimers are then used to estimate the incremental binding energies. We have applied this method to measure the binding energies of cyclic water clusters from the dimer to the tetramer. We obtain measured values of D(0) that are in agreement with theoretical estimates to within ∼20%. Our results suggest that this threshold-based approach should be generally applicable using either mass spectrometry or optical spectroscopy techniques for detection, provided that the clusters selected for study are at least as strongly bound as those of water, and that a peak in the overall spectrum of the beam corresponding only to the cluster chosen (at least in the vicinity of the threshold) can be located.
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Affiliation(s)
- William K Lewis
- University of Dayton Research Institute, Dayton, Ohio 45469, USA.
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Ramilowski JA, Farrelly D. Fixed node diffusion Monte Carlo using a genetic algorithm: a study of the CO-(4)He(N) complex, N = 1…10. Phys Chem Chem Phys 2012; 14:8123-36. [PMID: 22538980 DOI: 10.1039/c2cp40541e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The diffusion Monte Carlo (DMC) method is a widely used algorithm for computing both ground and excited states of many-particle systems; for states without nodes the algorithm is numerically exact. In the presence of nodes approximations must be introduced, for example, the fixed-node approximation. Recently we have developed a genetic algorithm (GA) based approach which allows the computation of nodal surfaces on-the-fly [Ramilowski and Farrelly, Phys. Chem. Chem. Phys., 2010, 12, 12450]. Here GA-DMC is applied to the computation of rovibrational states of CO-(4)He(N) complexes with N≤ 10. These complexes have been the subject of recent high resolution microwave and millimeter-wave studies which traced the onset of microscopic superfluidity in a doped (4)He droplet, one atom at a time, up to N = 10 [Surin et al., Phys. Rev. Lett., 2008, 101, 233401; Raston et al., Phys. Chem. Chem. Phys., 2010, 12, 8260]. The frequencies of the a-type (microwave) series, which correlate with end-over-end rotation in the CO-(4)He dimer, decrease from N = 1 to 3 and then smoothly increase. This signifies the transition from a molecular complex to a quantum solvated system. The frequencies of the b-type (millimeter-wave) series, which evolves from free rotation of the rigid CO molecule, initially increase from N = 0 to N∼ 6 before starting to decrease with increasing N. An interesting feature of the b-type series, originally observed in the high resolution infra-red (IR) experiments of Tang and McKellar [J. Chem. Phys., 2003, 119, 754] is that, for N = 7, two lines are observed. The GA-DMC algorithm is found to be in good agreement with experimental results and possibly detects the small (∼0.7 cm(-1)) splitting in the b-series line at N = 7. Advantages and disadvantages of GA-DMC are discussed.
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Affiliation(s)
- Jordan A Ramilowski
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300, USA
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22
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Sartakov BG, Toennies JP, Vilesov AF. Infrared spectroscopy of carbonyl sulfide inside a pure3He droplet. J Chem Phys 2012; 136:134316. [DOI: 10.1063/1.3697475] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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23
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MARINETTI FABIO, BODO ENRICO, GIANTURCO FRANCOA. IONIC OH AS DOPANT OF HELIUM DROPLETS: AB INITIO POTENTIAL ENERGY SURFACES FOR OH+(3Σ-)-4He, OH-(1Σ-)-4He, AND STABLE STRUCTURES OF THEIR SMALLER CLUSTERS. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2011. [DOI: 10.1142/s0219633606002519] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Accurate, post-Hartree–Fock calculations have been carried out for a broad range of geometries in order to obtain an extended description of the orientational anisotropy and radial strength of the interaction of OH + and OH - ions with the unit species of a weak quantum solvent as that provided by 4 He droplets. The potential energy surfaces (PES) are obtained for the smallest complex system with one 4 He atom, and the possible role and importance of many-body effects is also investigated. The energetics and shapes of the OH +-4 He and OH --4 He internal bound states are obtained and analyzed in detail.
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Affiliation(s)
- FABIO MARINETTI
- Department of Chemistry, University of Rome La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy
| | - ENRICO BODO
- Department of Chemistry, University of Rome La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy
| | - FRANCO A. GIANTURCO
- Department of Chemistry, University of Rome La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy
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Pereiro M, Baldomir D, Arias JE. A first-principles study of the influence of helium atoms on the optical response of small silver clusters. J Chem Phys 2011; 134:084307. [PMID: 21361539 DOI: 10.1063/1.3556821] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Optical excitation spectra of Ag(n) and Ag(n)@He(60) (n = 2, 8) clusters are investigated in the framework of the time-dependent density functional theory (TDDFT) within the linear response regime. We have performed the ab initio calculations for two different exact exchange functionals (GGA-exact and LDA-exact). The computed spectra of Ag(n)@He(60) clusters with the GGA-exact functional accounting for exchange-correlation effects are found to be generally in a relatively good agreement with the experiment. A strategy is proposed to obtain the ground-state structures of the Ag(n)@He(60) clusters and in the initial process of the geometry optimization, the He environment is simulated with buckyballs. A redshift of the silver clusters spectra is observed in the He environment with respect to the ones of bare silver clusters. This observation is discussed and explained in terms of a contraction of the Ag-He bonding length and a consequent confinement of the s valence electrons in silver clusters. Likewise, the Mie-Gans predictions combined with our TDDFT calculations also show that the dielectric effect produced by the He matrix is considerably less important in explaining the redshifting observed in the optical spectra of Ag(n)@He(60) clusters.
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Affiliation(s)
- M Pereiro
- Departamento de Física Aplicada, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.
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25
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Suárez AG, Ramilowski JA, Benito R, Farrelly D. Renormalization of the rotational constants of an ammonia molecule seeded into a 4He droplet. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2010.12.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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26
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Denifl S, Zappa F, Mähr I, Mauracher A, Probst M, Urban J, Mach P, Bacher A, Bohme DK, Echt O, Märk TD, Scheier P. Ionization of doped helium nanodroplets: complexes of C60 with water clusters. J Chem Phys 2010; 132:234307. [PMID: 20572705 DOI: 10.1063/1.3436721] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Water clusters are known to undergo an autoprotonation reaction upon ionization by photons or electron impact, resulting in the formation of (H(2)O)(n)H(3)O(+). Ejection of OH cannot be quenched by near-threshold ionization; it is only partly quenched when clusters are complexed with inert gas atoms. Mass spectra recorded by electron ionization of water-doped helium droplets show that the helium matrix also fails to quench OH loss. The situation changes drastically when helium droplets are codoped with C(60). Charged C(60)-water complexes are predominantly unprotonated; C(60)(H(2)O)(4)(+) and (C(60))(2)(H(2)O)(4)(+) appear with enhanced abundance. Another intense ion series is due to C(60)(H(2)O)(n)OH(+); dehydrogenation is proposed to be initiated by charge transfer between the primary He(+) ion and C(60). The resulting electronically excited C(60)(+*) leads to the formation of a doubly charged C(60)-water complex either via emission of an Auger electron from C(60)(+*), or internal Penning ionization of the attached water complex, followed by charge separation within {C(60)(H(2)O)(n)}(2+). This mechanism would also explain previous observations of dehydrogenation reactions in doped helium droplets. Mass-analyzed ion kinetic energy scans reveal spontaneous (unimolecular) dissociation of C(60)(H(2)O)(n)(+). In addition to the loss of single water molecules, a prominent reaction channel yields bare C(60)(+) for sizes n=3, 4, or 6. Ab initio Hartree-Fock calculations for C(60)-water complexes reveal negligible charge transfer within neutral complexes. Cationic complexes are well described as water clusters weakly bound to C(60)(+). For n=3, 4, or 6, fissionlike desorption of the entire water complex from C(60)(H(2)O)(n)(+) energetically competes with the evaporation of a single water molecule.
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Affiliation(s)
- S Denifl
- Institut für Ionenphysik und Angewandte Physik and Center for Molecular Biosciences Innsbruck, Leopold Franzens Universität, 6020 Innsbruck, Austria
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27
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Heitz MC, Teixidor L, Van-Oanh NT, Spiegelman F. Relaxation Dynamics of Photoexcited Calcium Deposited on Argon Clusters: Theoretical Simulation of Time-Resolved Photoelectron Spectra. J Phys Chem A 2010; 114:3287-96. [DOI: 10.1021/jp909443p] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Marie-Catherine Heitz
- Laboratoire de Chimie et de Physique Quantiques, IRSAMC, CNRS and Université de Toulouse, Université Paul Sabatier, 118 route de Narbonne, 31062, Toulouse,Cedex, France, Laboratoire de Chimie Physique, CNRS and Université Paris XI, 91405 Orsay, France
| | - Laurent Teixidor
- Laboratoire de Chimie et de Physique Quantiques, IRSAMC, CNRS and Université de Toulouse, Université Paul Sabatier, 118 route de Narbonne, 31062, Toulouse,Cedex, France, Laboratoire de Chimie Physique, CNRS and Université Paris XI, 91405 Orsay, France
| | - Nguyen-Thi Van-Oanh
- Laboratoire de Chimie et de Physique Quantiques, IRSAMC, CNRS and Université de Toulouse, Université Paul Sabatier, 118 route de Narbonne, 31062, Toulouse,Cedex, France, Laboratoire de Chimie Physique, CNRS and Université Paris XI, 91405 Orsay, France
| | - Fernand Spiegelman
- Laboratoire de Chimie et de Physique Quantiques, IRSAMC, CNRS and Université de Toulouse, Université Paul Sabatier, 118 route de Narbonne, 31062, Toulouse,Cedex, France, Laboratoire de Chimie Physique, CNRS and Université Paris XI, 91405 Orsay, France
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28
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Whitley HD, DuBois JL, Whaley KB. Spectral shifts and helium configurations in 4He(N)-tetracene clusters. J Chem Phys 2009; 131:124514. [PMID: 19791901 DOI: 10.1063/1.3236386] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Spectral shifts of electronic transitions of tetracene in helium droplets are investigated in a theoretical study of (4)He(N)-tetracene clusters with 1 < or = N < or = 150. Utilizing a pairwise interaction for the S(0) state of tetracene with helium that is extended by semiempirical terms to construct a potential for the S(1) state of tetracene with helium, the spectral shift is calculated from path integral Monte Carlo calculations of the helium equilibrium properties with tetracene in the S(0) and S(1) states at T = 0 and at T = 0.625 K. The calculated spectral shifts are in quantitative agreement with available experimental measurements for small values of N (< or = 8) at T approximately 0.4 K and show qualitative agreement for larger N (10-20). The extrapolated value of the spectral shift in large droplets (N approximately 10(4)) is approximately 90% of the experimentally measured value. We find no evidence of multiple configurations of helium for any cluster size for either the S(0) or S(1) state of tetracene. These results suggest that the observed spectral splitting of electronic transitions of tetracene in large helium droplets is not due to the coexistence of static metastable helium densities, unlike the situation previously analyzed for the phthalocyanine molecule.
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Affiliation(s)
- Heather D Whitley
- Department of Chemistry and Kenneth S. Pitzer Center for Theoretical Chemistry, University of California, Berkeley, California 94720, USA.
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29
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Ferreira da Silva F, Waldburger P, Jaksch S, Mauracher A, Denifl S, Echt O, Märk TD, Scheier P. On the size of ions solvated in helium clusters. Chemistry 2009; 15:7101-8. [PMID: 19533729 DOI: 10.1002/chem.200802554] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Helium nanodroplets are doped with SF(6), C(4)F(8), CCl(4), C(6)H(5)Br, CH(3)I, and I(2). Upon interaction with free electrons a variety of positively and negatively charged cluster ions X(+/-)He(n) are observed where X(+/-) = F(+/-), Cl(+/-), Br(+/-), I(+), I(2) (+), or CH(3)I(+). The yield of these ions versus cluster size n drops at characteristic sizes n(s) that range from n(s) = 10.2+/-0.6 for F(+) to n(s) = 22.2+/-0.2 for Br(-). n(s) values for halide anions are about 70% larger than for the corresponding cations. The steps in the ion yield suggest closure of the first solvation shell. We propose a simple classical model to estimate ionic radii from n(s). Assuming the helium density in the first solvation shell equals the helium bulk density one finds that radii of halide anions in helium are nearly twice as large as in alkali halide crystals, indicating the formation of an anion bubble due to the repulsive forces that derive from the exchange interaction. In spite of the simplicity of our model, anion radii derived from it agree within approximately 10% with values derived from the mobility of halide anions in superfluid bulk helium, and with values computed by quantum Monte Carlo methods for X(-)He(n) cluster anions.
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Affiliation(s)
- Filipe Ferreira da Silva
- Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universität, Technikerstrasse 25, 6020 Innsbruck, Austria
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30
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Jaksch S, Ferreira da Silva F, Denifl S, Echt O, Märk TD, Scheier P. Experimental evidence for the existence of an electronically excited state of the proposed dihydrogen radical cation He-H-H-He+. Chemistry 2009; 15:4190-4. [PMID: 19248067 DOI: 10.1002/chem.200802545] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Survival of the weakest: The existence of a new class of centrosymmetric radical cations in which H(2) bridges two identical main group elements was recently proposed in this journal by Uggerud and co-workers. By growing complexes inside helium nanodroplets at subkelvin temperatures, we obtained experimental evidence for the existence of the most weakly bound member of this class, He-H-H-He(+) (see picture), although in a metastable, electronically excited state.In a recent report, Uggerud and co-workers (A. Krapp et al., Chem. Eur. J. 2008, 14, 4028) proposed the existence of a new class of radical cations in which a dihydrogen bridges two identical main group elements. Upon electron impact ionization of helium nanodroplets doped with one or more H(2) molecules we observe various He(x)H(y) (+) cluster ions, including He(2)H(2) (+), which would belong to the proposed class of radical cations. Mass-analyzed kinetic energy scans reveal that the ion is metastable; it dissociates in the field-free region of the mass spectrometer. One reaction is into HeH(2) (+) + He with a low kinetic energy release of 15+/-4 meV. Surprisingly, another unimolecular reaction is observed, into HeH(+) + HeH (or He + H). The probability of this reaction is an order of magnitude higher, and the average kinetic energy release is four times larger. These findings suggest the presence of a metastable electronically excited state; they are consistent with the proposed linear, centrosymmetric ion structure of He-H-H-He(+).
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Affiliation(s)
- Stefan Jaksch
- Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universität, Technikerstrasse 25, 6020 Innsbruck, Austria
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31
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Lewis WK, Lindsay CM, Miller RE. Ionization and fragmentation of isomeric van der Waals complexes embedded in helium nanodroplets. J Chem Phys 2009; 129:201101. [PMID: 19045843 DOI: 10.1063/1.3025917] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ionization and charge transfer processes, which occur when a doped helium droplet undergoes electron impact, are studied for droplets doped with van der Waals complexes with various structures and electrostatic moments. The mass spectra of the two isomers of hydrogen cyanide complexed with either cyanoacetylene or acetylene in helium droplets were obtained using optically selected mass spectrometry, and show that the structure of the complex has a large effect on the fragmentation pattern. The resulting fragmentation pattern is consistent with an ionization process in which charge steering strongly influences the site of initial ionization. The observed dissociation products may also be subject to caging by the helium matrix.
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Affiliation(s)
- William K Lewis
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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32
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De Dea S, Miller DR, Continetti RE. Cluster and Solute Velocity Distributions in Free-Jet Expansions of Supercritical CO2. J Phys Chem A 2008; 113:388-98. [DOI: 10.1021/jp805618z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Silvia De Dea
- Department of Mechanical and Aerospace Engineering and Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0001
| | - David R. Miller
- Department of Mechanical and Aerospace Engineering and Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0001
| | - Robert E. Continetti
- Department of Mechanical and Aerospace Engineering and Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0001
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33
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Wang CC, Kornilov O, Gessner O, Kim JH, Peterka DS, Neumark DM. Photoelectron Imaging of Helium Droplets Doped with Xe and Kr Atoms. J Phys Chem A 2008; 112:9356-65. [DOI: 10.1021/jp802332f] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chia C. Wang
- Department of Chemistry, University of California, Berkeley, California 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Oleg Kornilov
- Department of Chemistry, University of California, Berkeley, California 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Oliver Gessner
- Department of Chemistry, University of California, Berkeley, California 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Jeong Hyun Kim
- Department of Chemistry, University of California, Berkeley, California 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Darcy S. Peterka
- Department of Chemistry, University of California, Berkeley, California 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Daniel M. Neumark
- Department of Chemistry, University of California, Berkeley, California 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
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Coccia E, Marinetti F, Bodo E, Gianturco FA. Chemical solutions in a quantum solvent: anionic electrolytes in 4He nanodroplets. Chemphyschem 2008; 9:1323-30. [PMID: 18461589 DOI: 10.1002/cphc.200800132] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Variational and diffusion Monte Carlo (VMC and DMC) calculations are presented for anionic electrolytes solvated in (4)He. The electrolytes have the general structure X(-)(He)(N), with X=F, Cl, Br and I, and N varying up to 40 (41 for I(-)). The overall interaction potential is obtained from accurate ab initio data for the two-body components and then using the sum-of-potentials approximation. Our computational scheme is a robust procedure, giving us accurate trial wavefunctions that can be used to perform high-quality DMC calculations. The results indicate very marked delocalization and permanence of the liquid-like quantum features of the solvent adatoms surrounding the anionic impurities. This finding stands in contrast to the more structured, solid-like behavior of the quantum solutions with alkali metal cations embedded in He nanodroplets. While other negatively charged species such as H(-) have shown an overall repulsive interaction with He, the present calculations clearly indicate that the halogen anions remain solvated within liquid-like solvent "bubbles" of species-dependent size.
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Affiliation(s)
- Emanuele Coccia
- Department of Chemistry and CNISM, University of Rome La Sapienza, Piazzale A. Moro, 00185 Rome, Italy.
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Nagl J, Auböck G, Hauser AW, Allard O, Callegari C, Ernst WE. High-spin alkali trimers on helium nanodroplets: Spectral separation and analysis. J Chem Phys 2008; 128:154320. [DOI: 10.1063/1.2906120] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Bonhommeau D, Lewerenz M, Halberstadt N. Fragmentation of ionized doped helium nanodroplets: theoretical evidence for a dopant ejection mechanism. J Chem Phys 2008; 128:054302. [PMID: 18266445 DOI: 10.1063/1.2823101] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report a theoretical study of the effect induced by a helium nanodroplet environment on the fragmentation dynamics of a dopant. The dopant is an ionized neon cluster Ne(n) (+) (n=4-6) surrounded by a helium nanodroplet composed of 100 atoms. A newly designed mixed quantum/classical approach is used to take into account both the large helium cluster zero-point energy due to the light mass of the helium atoms and all the nonadiabatic couplings between the Ne(n) (+) potential-energy surfaces. The results reveal that the intermediate ionic dopant can be ejected from the droplet, possibly with some helium atoms still attached, thereby reducing the cooling power of the droplet. Energy relaxation by helium atom evaporation and dissociation, the other mechanism which has been used in most interpretations of doped helium cluster dynamics, also exhibits new features. The kinetic energy distribution of the neutral monomer fragments can be fitted to the sum of two Boltzmann distributions, one with a low kinetic energy and the other with a higher kinetic energy. This indicates that cooling by helium atom evaporation is more efficient than was believed so far, as suggested by recent experiments. The results also reveal the predominance of Ne(2) (+) and He(q)Ne(2) (+) fragments and the absence of bare Ne(+) fragments, in agreement with available experimental data (obtained for larger helium nanodroplets). Moreover, the abundance in fragments with a trimeric neon core is found to increase with the increase in dopant size. Most of the fragmentation is achieved within 10 ps and the only subsequent dynamical process is the relaxation of hot intermediate He(q)Ne(2) (+) species to Ne(2) (+) by helium atom evaporation. The dependence of the ionic fragment distribution on the parent ion electronic state reached by ionization is also investigated. It reveals that He(q)Ne(+) fragments are produced only from the highest electronic state, whereas He(q)Ne(2) (+) fragments originate from all the electronic states. Surprisingly, the highest electronic states also lead to fragments that still contain the original ionic dopant species. A mechanism is conjectured to explain this fragmentation inhibition.
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Affiliation(s)
- D Bonhommeau
- University of Minnesota, 207 Pleasant Street S.E., 230 Smith Hall, Minneapolis, Minnesota 55455-0431, USA
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Denifl S, Zappa F, Mähr I, Mauracher A, Probst M, Märk TD, Scheier P. Inelastic electron interaction with chloroform clusters embedded in helium droplets. J Am Chem Soc 2008; 130:5065-71. [PMID: 18335985 DOI: 10.1021/ja075972m] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The inelastic electron interaction (ionization/attachment) with chloroform embedded in helium droplets has been studied utilizing a two-sector field mass spectrometer. Positive mass spectra have been recorded at the electron energy of 70 eV and are compared with previous results in the gas phase and with other systems embedded in helium droplets. Moreover, the negative ion mass spectrum has been recorded at the electron energy of 1.5 eV. Both negative and positive mass spectra show that chloroform clusters are easily formed by embedding single molecules in the helium droplets. Moreover, for anions appearing in the mass spectrum, the ion yield has been determined as function of the electron energy. While no parent anion of chloroform can be observed in the gas phase, the present cluster environment allows the stabilization of the transient negative ion. The influence of the helium droplet upon the ionization or attachment process of the embedded chloroform is discussed.
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Affiliation(s)
- Stephan Denifl
- Institut für Ionenphysik and Angewandte Physik and Center for Molecular Biosciences Innsbruck, Leopold-Franzens Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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Pacheco AB, Thorndyke B, Reyes A, Micha DA. Quantum dynamics of an excited alkali atom in a noble gas cluster: Lithium attached to a helium cluster. J Chem Phys 2007; 127:244504. [DOI: 10.1063/1.2813889] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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39
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Mozhayskiy V, Slipchenko MN, Adamchuk VK, Vilesov AF. Use of helium nanodroplets for assembly, transport, and surface deposition of large molecular and atomic clusters. J Chem Phys 2007; 127:094701. [PMID: 17824753 DOI: 10.1063/1.2759927] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The utility of continuous beam of helium droplets for assembly, transport, and surface deposition of metal and molecular clusters is studied. Clusters of propyne having from about 10 to 10(4) molecules were obtained via sequential pickup of molecules by He droplets with average sizes in the range of 10(4)-10(7) atoms. The maximum attainable flux of the propyne molecules carried by He droplets was found to be in the range of (5-15)x10(15) molecules sr(-1) s(-1), being larger in larger droplets. The size of the clusters and the flux of the transported species are ultimately limited by the evaporative extinction of the entire helium droplet upon capture of particles. It is shown that the attenuation of the He droplet beam in the process of the cluster growth can be used in order to obtain the average size and the binding energy of the clusters. Furthermore, we used He droplets for assembling and surface deposition of gold and silver clusters having about 500 atoms. Typical deposition rate of metal atoms of about 3 x 10(15) atoms sr(-1) s(-1) is comparable to or larger than obtained with other beam deposition techniques. We propose that doping of He droplets by Au and Ag atoms in two separate pickup chambers leads to formation of the bimetal clusters having core-shell structure.
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Affiliation(s)
- Vadim Mozhayskiy
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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Ramilowski JA, Mikosz AA, Farrelly D, Fajín JLC, Fernández B. Rotational Structure of Small 4He Clusters Seeded with HF, HCl, and HBr Molecules. J Phys Chem A 2007; 111:12275-88. [DOI: 10.1021/jp0746143] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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41
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Braun A, Drabbels M. Photodissociation of alkyl iodides in helium nanodroplets. I. Kinetic energy transfer. J Chem Phys 2007; 127:114303. [PMID: 17887833 DOI: 10.1063/1.2767261] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The photodissociation of (fluorinated) alkyl iodides in helium nanodroplets at a wavelength of 266 nm has been investigated by means of ion imaging techniques. It is found that a significant fraction of the created fragments escapes from the helium droplets. The speed and kinetic energy distributions of these fragments are found to be notably modified with respect to the corresponding gas phase distributions. The fragments, furthermore, show a speed dependent angular distribution. The loss of kinetic energy as well as the reduction of the anisotropy parameter show a strong mass dependence. These observations point to a nonthermal escape process in which the kinetic energy and momentum transfer from the fragments to the solvent is governed by binary collisions with the individual helium atoms making up the droplet. Monte Carlo simulations based on hard-sphere binary collisions substantiate this interpretation of the data.
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Affiliation(s)
- Andreas Braun
- Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédéral de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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42
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Peterka DS, Kim JH, Wang CC, Poisson L, Neumark DM. Photoionization Dynamics in Pure Helium Droplets. J Phys Chem A 2007; 111:7449-59. [PMID: 17571863 DOI: 10.1021/jp0710032] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photoionization and photoelectron spectroscopy of pure He droplets were investigated at photon energies between 24.6 eV (the ionization energy of He) and 28.0 eV. Time-of-flight mass spectra and photoelectron images were obtained at a series of molecular beam source temperatures and pressures to assess the effect of droplet size on the photoionization dynamics. At source temperatures below 16 K, where there is significant production of clusters with more than 10(4) atoms, the photoelectron images are dominated by fast electrons produced via direct ionization, with a small contribution from very slow electrons with kinetic energies below 1 meV arising from an indirect mechanism. The fast photoelectrons from the droplets have as much as 0.5 eV more kinetic energy than those from atomic He at the same photon energy. This result is interpreted and simulated within the context of a "dimer model", in which one assumes vertical ionization from two nearest-neighbor He atoms to the attractive region of the He2+ potential energy curve. Possible mechanisms for the slow electrons, which were also seen at energies below IE(He), are discussed, including vibrational autoionizaton of Rydberg states comprising an electron weakly bound to the surface of a large HeN+ core.
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Affiliation(s)
- Darcy S Peterka
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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43
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Küpper J, Merritt JM. Spectroscopy of free radicals and radical containing entrance-channel complexes in superfluid helium nanodroplets. INT REV PHYS CHEM 2007. [DOI: 10.1080/01442350601087664] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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44
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Whitley HD, Huang P, Kwon Y, Whaley KB. Multiple solvation configurations around phthalocyanine in helium droplets. J Chem Phys 2007; 123:054307. [PMID: 16108639 DOI: 10.1063/1.1961532] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Recent measurements of the emission spectrum of phthalocyanine solvated in superfluid helium nanodroplets exhibit a constant 10.3 cm(-1) splitting of each emission line relative to the absorption spectrum. This splitting has been attributed to two distinct helium environments near the surface of the phthalocyanine molecule. Rigid-body path-integral Monte Carlo provides a means of investigating the origin of the splitting on a detailed microscopic level. Path-integral Monte Carlo simulations of 4He(N)-phthalocyanine at 0.625 K with N ranging from 24 to 150 show two distinct helium configurations. One configuration is commensurate with the molecular substrate and the other is a triangular lattice. We investigate the energetics of these two configurations and use a method for calculating electronic spectral shifts for aromatic molecule-rare-gas clusters due to dispersive interactions to estimate the spectral splitting that would arise from the two helium configurations seen for N=150. The results are in reasonable agreement with the experimentally measured splitting, supporting the existence of two distinct local helium environments near the surface of the molecule in the nanodroplets.
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Affiliation(s)
- Heather D Whitley
- Department of Chemistry and Kenneth S. Pitzer Center for Theoretical Chemistry, University of California, Berkeley, California 94720, USA.
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Bonhommeau D, Lake PT, Le Quiniou C, Lewerenz M, Halberstadt N. Modeling the fragmentation dynamics of ionic clusters inside helium nanodroplets: The case of He100Ne4+. J Chem Phys 2007; 126:051104. [PMID: 17302465 DOI: 10.1063/1.2515225] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
We present simulation results on the effect of a helium nanodroplet environment on the fragmentation dynamics of embedded molecular systems. The helium atoms are treated explicitly, with zero-point effects taken into account through an effective helium-helium interaction potential. The ionized neon tetramer is used as a model molecular system because, like all the small rare-gas clusters, it fragments extensively upon ionization. All the nonadiabatic effects between electronic states of the ionized neon cluster are taken into account. The results reveal a predominance of Ne2+ and HepNe2+ fragments and the absence of bare Ne+ fragments, in agreement with available experimental data. The neutral monomer fragments exhibit a rather wide kinetic energy distribution that can be fitted to the sum of two Boltzmann distributions, one with a low kinetic energy and the other with a higher kinetic energy. This indicates that cooling by helium atom evaporation is more efficient than was believed so far, as suggested by recent experimental results. Purely classical calculations are shown to strongly overestimate the amount of cage effect (cooling), clearly indicating the need to take into account zero-point effects.
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Affiliation(s)
- D Bonhommeau
- Laboratoire de Chimie et de Physique Quantiques, IRSAMC, UMR 5626, CNRS et Université Paul Sabatier, 118 route de Narbonne, F-31062 Toulouse Cedex 09, France
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46
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Marinetti F, Bodo E, Gianturco FA. Microsolvation of an Ionic Dopant in Small4He Clusters: OH+(3Σ)(4He)N via Genetic Algorithm Optimizations. Chemphyschem 2007; 8:93-100. [PMID: 17121409 DOI: 10.1002/cphc.200600440] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The optimized spatial structures of the small clusters (with N up to 33) formed by an increasing number of (4)He atoms, which act as a microsolvent surrounding the OH(+) ionic molecular dopant, are obtained using a sum-of-potentials scheme corrected by three-body (3B) effects. The most stable structures are generated using the type of genetic algorithm described herein, and the sequential formation of regular shell structures is analyzed in detail. Possible quantum corrections for both the solvent distributions and the stable energetics are analyzed and discussed.
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Affiliation(s)
- Fabio Marinetti
- Department of Chemistry and CNISM, University of Rome La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy
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47
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Tiggesbäumker J, Stienkemeier F. Formation and properties of metal clusters isolated in helium droplets. Phys Chem Chem Phys 2007; 9:4748-70. [PMID: 17712454 DOI: 10.1039/b703575f] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The unique conditions forming atomic and molecular complexes and clusters using superfluid helium nanodroplets have opened up an innovative route for studying the physical and chemical properties of matter on the nanoscale. This review summarizes the specific characteristics of the formation of atomic clusters partly generated far from equilibrium in the helium environment. Special emphasis is on the optical response, electronic properties as well as dynamical processes which are mostly affected by the surrounding quantum matrix. Experiments include the optical induced response of isolated cluster systems in helium under quite different excitation conditions ranging from the linear regime up to the violent interaction with a strong laser field leading to Coulomb explosion and the generation of highly charged atomic fragments. The variety of results on the outstanding properties in the quantum size regime highlights the peculiar capabilities of helium nanodroplet isolation spectroscopy.
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48
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El Hadj Rhouma MB, Ben Lakhdar Z, Berriche H, Spiegelman F. Rydberg states of small NaArn* clusters. J Chem Phys 2006; 125:084315. [PMID: 16965020 DOI: 10.1063/1.2229210] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The 4s and 5s Rydberg excited states of NaAr(n)* clusters are investigated using a pseudopotential quantum-classical method. While NaAr(n) clusters in their ground state are known to be weakly bound van der Waals complexes with Na lying at the surface of the argon cluster, isomers in 4s or 5s electronically excited states of small NaAr(n)* clusters (n< or =10) are found to be stable versus dissociation. The relationship between electronic excitation and cluster geometry is analyzed as a function of cluster size. For both 4s and 5s states, the stable exciplex isomers essentially appear as sodium-centered structures with similar topologies, converging towards those of the related NaAr(n)+ positive ions when the excitation level is increased. This is consistent with a Rydberg-type picture for the electronically excited cluster, described by a central sodium ion solvated by an argon shell, and an outer diffuse electron orbiting around this NaAr(n)+ cluster core.
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Affiliation(s)
- M Ben El Hadj Rhouma
- Laboratoire d'Etudes des Milieux Ionisés et Réactifs (EMIR), Institut Préparatoire aux Etudes d'Ingénieurs, 5019 Monastir, Tunisia
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Stiles PL, Miller RE. Structures and Bonding Nature of Small Monoligated Copper Clusters (HCN−Cun, n = 1−3) through High-Resolution Infrared Spectroscopy and Theory. J Phys Chem A 2006; 110:10225-35. [PMID: 16928112 DOI: 10.1021/jp063187a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The structures, C-H stretching frequencies, and dipole moments of HCN-Cun (n = 1-3) clusters are determined through high-resolution infrared spectroscopy. The complexes are formed and probed within superfluid helium droplets, whereby the helium droplet beam is passed over a resistively heated crucible containing copper shot and then through a gas HCN pickup cell. All complexes are found to be bound to the nitrogen end of the HCN molecule and on the "atop site" of the copper cluster. Through the experimental C-H vibrational shifts of HCN-Cun and ab initio calculations, it was found that the HCN-metal interaction changes from a strong van der Waals bond in n = 1 to a partially covalent bond in HCN-Cu3. Comparisons with existing infrared data on copper surfaces show that the HCN-Cun bond must begin to weaken at very large copper cluster sizes, eventually returning to a van der Waals bond in the bulk copper surface case.
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Affiliation(s)
- Paul L Stiles
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599
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50
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Denifl S, Zappa F, Mähr I, Lecointre J, Probst M, Märk TD, Scheier P. Mass spectrometric investigation of anions formed upon free electron attachment to nucleobase molecules and clusters embedded in superfluid helium droplets. PHYSICAL REVIEW LETTERS 2006; 97:043201. [PMID: 16907571 DOI: 10.1103/physrevlett.97.043201] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2006] [Indexed: 05/11/2023]
Abstract
Here we report the first mass spectrometric study of negative ions formed via free electron attachment (EA) to nucleobases (NBs) embedded in helium clusters. Pure and mixed clusters of adenine and thymine have been formed by pickup of isolated NB molecules by cold helium droplets. In contrast to EA of isolated molecules in the gas phase we observe a long-lived parent anion NB- and, in addition, parent cluster ions NB-n up to size n=6. Moreover, we show that a low energy electron penetrating into a doped helium droplet causes efficient damage of the embedded nucleobases via resonant, site selective, dissociative electron attachment.
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Affiliation(s)
- Stephan Denifl
- Institut für Ionenphysik und Angewandte Physik and Center for Molecular Biosciences Innsbruck, Leopold Franzens Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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