1
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Topcu G, Al Hindawi AMA, Feng C, Spence D, Sitorus B, Liu H, Ellis AM, Yang S. Precision engineering of nano-assemblies in superfluid helium by the use of van der Waals forces. Commun Chem 2024; 7:125. [PMID: 38834741 DOI: 10.1038/s42004-024-01203-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 05/16/2024] [Indexed: 06/06/2024] Open
Abstract
The ability to precisely engineer nanostructures underpins a wide range of applications in areas such as electronics, optics, and biomedical sciences. Here we present a novel approach for the growth of nanoparticle assemblies that leverages the unique properties of superfluid helium. Unlike viscous solvents at or near room temperature, superfluid helium provides an unperturbed and cold environment in which weak van der Waals interactions between molecular templates and metal atoms become significant and can define the spatial arrangement of nanoparticles. To demonstrate this concept, diol and porphyrin-based molecules are employed as templates to grow gold nanoparticle assemblies in superfluid helium droplets. After soft-landing on a solid surface to remove the helium, transmission electron microscopy (TEM) imaging shows the growth of gold nanoparticles at specific binding sites within the molecular templates where the interaction between gold atoms and the molecular template is at its strongest.
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Affiliation(s)
- Gokhan Topcu
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Aula M A Al Hindawi
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
- Department of Chemistry, College of Education for Pure Science, University of Karbala, Karbala, Iraq
| | - Cheng Feng
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Daniel Spence
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Berlian Sitorus
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
- Department of Chemistry, Tanjungpura University, Pontianak, Indonesia
| | - Hanqing Liu
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Andrew M Ellis
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Shengfu Yang
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK.
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2
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Kranabetter L, Kristensen HH, Schouder CA, Stapelfeldt H. Structure determination of alkali trimers on helium nanodroplets through laser-induced Coulomb explosion. J Chem Phys 2024; 160:131101. [PMID: 38557840 DOI: 10.1063/5.0200389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Accepted: 03/15/2024] [Indexed: 04/04/2024] Open
Abstract
Alkali trimers, Ak3, located on the surface of He nanodroplets are triply ionized following multiphoton absorption from an intense femtosecond laser pulse, leading to fragmentation into three correlated Ak+ ions. Combining the information from threefold covariance analysis of the emission direction of the fragment ions and their kinetic energy distributions P(Ekin), we find that Na3, K3, and Rb3 have an equilateral triangular structure, corresponding to that of the lowest lying quartet state A2'4, and determine the equilibrium bond distance Req(Na3) = 4.65 ± 0.15 Å, Req(K3) = 5.03 ± 0.18 Å, and Req(Rb3) = 5.45 ± 0.22 Å. For K3 and Rb3, these values agree well with existing theoretical calculations, while for Na3, the value is 0.2-0.3 Å larger than the existing theoretical results. The discrepancy is ascribed to a minor internuclear motion of Na3 during the ionization process. In addition, we determine the distribution of internuclear distances P(R) under the assumption of fixed bond angles. The results are compared to the square of the internuclear wave function |Ψ(R)|2.
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Affiliation(s)
- Lorenz Kranabetter
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Henrik H Kristensen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
| | - Constant A Schouder
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
- LIDYL, CNRS, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
| | - Henrik Stapelfeldt
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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3
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Karachi SS, Eskandari K. Bonding in the high spin lithium clusters: Non-nuclear attractors play a crucial role. J Comput Chem 2023; 44:962-968. [PMID: 36573786 DOI: 10.1002/jcc.27056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 11/29/2022] [Accepted: 12/01/2022] [Indexed: 12/28/2022]
Abstract
The bonding in lithium high-spin clusters contradicts the usual chemical bonding concept since there are no electron pairs between the atoms, and they are bound with parallel spin electrons. Quantum theory of atoms in molecules and interacting quantum atom analysis (IQA) were used to investigate the nature of bonding in the high-spin Li n n + 1 n = 2 - 5 clusters. Our findings demonstrate that the non-nuclear attractors (NNAs) are an essential component of the high-spin lithium clusters and play a key role in keeping them stable. Based on IQA energy terms, an electrostatic destabilizing interaction between the lithium atoms works against the cluster formation. On the other hand, the interactions between lithium atoms and NNA basins are stabilizing and outweigh the lithium-lithium destabilizing effects. In fact, NNAs tend to draw lithium atoms together and stabilize the resulting cluster. The high-spin clusters of lithium can be regarded as electrostatically driven compounds since the electrostatic components are primarily responsible for the stabilizing interactions between NNAs and Li atoms. The only exception is 3 Li2 , which lacks NNA and has a non-repellent lithium-lithium interaction. Indeed, in the 3 Li2 , the interatomic electrostatic component is negligibly small, and the exchange-correlation term leads to a weak bonding interaction.
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Affiliation(s)
- Sara Sadat Karachi
- Department of Chemistry, Isfahan University of Technology, Isfahan, Iran
| | - Kiamars Eskandari
- Department of Chemistry, Isfahan University of Technology, Isfahan, Iran
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4
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Alić J, Messner R, Alešković M, Küstner F, Rubčić M, Lackner F, Ernst WE, Šekutor M. Diamondoid ether clusters in helium nanodroplets. Phys Chem Chem Phys 2023; 25:11951-11958. [PMID: 36942672 PMCID: PMC10155488 DOI: 10.1039/d3cp00489a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
Abstract
Diamondoid ethers were introduced into superfluid helium nanodroplets and the resulting clusters were analyzed by time-of-flight mass spectrometry. Clusters of higher abundances (magic number clusters) were identified and the corresponding potential cluster geometries were obtained from GFN2-xTB and DFT computations. We found that the studied diamondoid ethers readily self-assemble in helium nanodroplets and that London dispersion attraction between hydrocarbon subunits acts as a driving force for cluster formation. On the other hand, hydrogen bonding between ether oxygens and trace water molecules fosters the eventual breakdown of the initial supramolecular aggregate.
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Affiliation(s)
- Jasna Alić
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
| | - Roman Messner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Marija Alešković
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
| | - Florian Küstner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Mirta Rubčić
- Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10 000 Zagreb, Croatia
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Marina Šekutor
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
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5
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Kristensen HH, Kranabetter L, Schouder CA, Stapper C, Arlt J, Mudrich M, Stapelfeldt H. Quantum-State-Sensitive Detection of Alkali Dimers on Helium Nanodroplets by Laser-Induced Coulomb Explosion. PHYSICAL REVIEW LETTERS 2022; 128:093201. [PMID: 35302820 DOI: 10.1103/physrevlett.128.093201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/21/2022] [Accepted: 02/10/2022] [Indexed: 06/14/2023]
Abstract
Rubidium dimers residing on the surface of He nanodroplets are doubly ionized by an intense femtosecond laser pulse leading to fragmentation into a pair of Rb^{+} ions. We show that the kinetic energy of the Rb^{+} fragment ions can be used to identify dimers formed in either the X ^{1}Σ_{g}^{+} ground state or in the lowest-lying triplet state, a ^{3}Σ_{u}^{+}. From the experiment, we estimate the abundance ratio of dimers in the a and X states as a function of the mean droplet size and find values between 4∶1 and 5∶1. Our technique applies generally to dimers and trimers of alkali atoms, here also demonstrated for Li_{2}, Na_{2}, and K_{2}, and will enable femtosecond time-resolved measurements of their rotational and vibrational dynamics, possibly with atomic structural resolution.
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Affiliation(s)
- Henrik H Kristensen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
| | - Lorenz Kranabetter
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Constant A Schouder
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Christoph Stapper
- Faculty of Chemistry and Pharmacy, University of Würzburg, Am Hubland, Campus Süd, D-97074 Würzburg, Germany
| | - Jacqueline Arlt
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Marcel Mudrich
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
| | - Henrik Stapelfeldt
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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6
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Alić J, Messner R, Lackner F, Ernst WE, Šekutor M. London dispersion dominating diamantane packing in helium nanodroplets. Phys Chem Chem Phys 2021; 23:21833-21839. [PMID: 34554159 PMCID: PMC8494270 DOI: 10.1039/d1cp03380h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 09/16/2021] [Indexed: 11/21/2022]
Abstract
Diamantane clusters formed inside superfluid helium nanodroplets were analyzed by time-of-flight mass spectrometry. Distinct cluster sizes were identified as "magic numbers" and the corresponding feasible structures for clusters consisting of up to 19 diamantane molecules were derived from meta-dynamics simulations and subsequent DFT computations. The obtained interaction energies were attributed to London dispersion attraction. Our findings demonstrate that diamantane units readily form assemblies even at low pressures and near-zero Kelvin temperatures, confirming the importance of the intermolecular dispersion effect for condensation of matter.
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Affiliation(s)
- Jasna Alić
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
| | - Roman Messner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Marina Šekutor
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
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7
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Ernst WE, Hauser AW. Metal clusters synthesized in helium droplets: structure and dynamics from experiment and theory. Phys Chem Chem Phys 2020; 23:7553-7574. [PMID: 33057510 DOI: 10.1039/d0cp04349d] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Metal clusters have drawn continuous interest because of their high potential for the assembly of matter with special properties that may significantly differ from the corresponding bulk. Controlled combination of particular elements in one nanoparticle can increase the options for the creation of new materials for photonic, catalytic, or electronic applications. Superfluid helium droplets provide confinement and ultralow temperature, i.e. an ideal environment for the atom-by-atom aggregation of a new nanoparticle. This perspective presents a review of the current research progress on the synthesis of tailored metal and metal oxide clusters including core-shell designs, their characterization within the helium droplet beam, deposition on various solid substrates, and analysis via surface diagnostics. Special attention is given to the thermal properties of mixed metal clusters and questions about alloy formation on the nanoscale. Experimental results are accompanied by theoretical approaches employing computational chemistry, molecular dynamics simulations and He density functional theory.
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Affiliation(s)
- Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
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8
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Thaler B, Heim P, Treiber L, Koch M. Ultrafast photoinduced dynamics of single atoms solvated inside helium nanodroplets. J Chem Phys 2020; 152:014307. [PMID: 31914752 DOI: 10.1063/1.5130145] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Helium nanodroplets can serve as reaction containers for photoinduced time-resolved studies of cold, isolated molecular systems that are otherwise inaccessible. Recently, three different dynamical processes, triggered by photoexcitation of a single atom inside a droplet, were observed in their natural time scale: Expansion of the He solvation shell (He bubble) within 600 fs initiates a collective bubble oscillation with a ∼30 ps oscillation period, followed by dopant ejection after ∼60 ps. Here, we present a systematic investigation of these processes by combining time-resolved photoelectron and photoion spectroscopy with time-dependent He density functional theory simulations. By variation of the photoexcitation energy, we find that the full excess excitation energy, represented by the blue-shifted in-droplet excitation band, is completely transferred to the He environment during the bubble expansion. Surprisingly, we find that variation of the droplet size has only a minor influence on the ejection time, providing insight into the spatial distribution of the ground-state atoms before photoexcitation. Simulated particle trajectories after photoexcitation are in agreement with experimental observations and suggest that the majority of ground-state atoms are located at around 16 Å below the droplet surface. Bubble expansion and oscillation are purely local effects, depending only on the ultimate dopant environment. These solvation-induced dynamics will be superimposed on intramolecular dynamics of molecular systems, and a mechanistic description is fundamental for the interpretation of future experiments.
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Affiliation(s)
- Bernhard Thaler
- Graz University of Technology, Institute of Experimental Physics, Petersgasse 16, 8010 Graz, Austria
| | - Pascal Heim
- Graz University of Technology, Institute of Experimental Physics, Petersgasse 16, 8010 Graz, Austria
| | - Leonhard Treiber
- Graz University of Technology, Institute of Experimental Physics, Petersgasse 16, 8010 Graz, Austria
| | - Markus Koch
- Graz University of Technology, Institute of Experimental Physics, Petersgasse 16, 8010 Graz, Austria
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9
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Rincon L, Torres FJ, Zambrano CH, Becerra M, Burgos JL, Almeida R, Liu S. Stability of "No-Pair Ferromagnetic" Lithium Clusters. J Phys Chem A 2019; 123:9721-9728. [PMID: 31638808 DOI: 10.1021/acs.jpca.9b06721] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
High-spin lithium clusters, n+1Lin (n = 2-21), have been systematically studied by using density functional theory. Although these high-spin clusters have no bonding electron pairs, they are stable with respect to isolated atoms. A set of 42 density functional theory functionals were benchmarked against CCSD(T)/cc-pVQZ results for clusters from the dimer to the hexamer. For these clusters, the strong non-additivity on the binding energy is analyzed employing a many-body energy decomposition scheme, concluding that most of the binding energy is due to a balance between the three- and four-body contributions. After a quality parameter had been defined, the LC-BP86 functional was identified as the most promising one for the description of high-spin lithium clusters. We employ the dependence of the second energy difference on cluster size to predict the formation of a higher-stability cluster.
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Affiliation(s)
- Luis Rincon
- Universidad San Francisco de Quito (USFQ) , Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Ingeniería Química, and Instituto de Simulación Computacional (ISC-USFQ) , Diego de Robles y Via Interoceanica , Quito , Ecuador 17-1200-841.,Universidad de Los Andes (ULA) , Departamento de Química, Facultad de Ciencias , La Hechicera, Mérida 5101 , Venezuela
| | - F Javier Torres
- Universidad San Francisco de Quito (USFQ) , Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Ingeniería Química, and Instituto de Simulación Computacional (ISC-USFQ) , Diego de Robles y Via Interoceanica , Quito , Ecuador 17-1200-841
| | - Cesar H Zambrano
- Universidad San Francisco de Quito (USFQ) , Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Ingeniería Química, and Instituto de Simulación Computacional (ISC-USFQ) , Diego de Robles y Via Interoceanica , Quito , Ecuador 17-1200-841
| | - Marcos Becerra
- Universidad San Francisco de Quito (USFQ) , Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Ingeniería Química, and Instituto de Simulación Computacional (ISC-USFQ) , Diego de Robles y Via Interoceanica , Quito , Ecuador 17-1200-841
| | - Jose Luis Burgos
- Universidad de Los Andes (ULA) , Departamento de Química, Facultad de Ciencias , La Hechicera, Mérida 5101 , Venezuela
| | - Rafael Almeida
- Universidad de Los Andes (ULA) , Departamento de Química, Facultad de Ciencias , La Hechicera, Mérida 5101 , Venezuela
| | - Shubin Liu
- Research Computing Center , University of North Carolina , Chapel Hill , North Carolina 27599-3420 , United States
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10
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Bruder L, Bangert U, Binz M, Uhl D, Vexiau R, Bouloufa-Maafa N, Dulieu O, Stienkemeier F. Coherent multidimensional spectroscopy of dilute gas-phase nanosystems. Nat Commun 2018; 9:4823. [PMID: 30446649 PMCID: PMC6240067 DOI: 10.1038/s41467-018-07292-w] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 10/25/2018] [Indexed: 12/20/2022] Open
Abstract
Two-dimensional electronic spectroscopy (2DES) is one of the most powerful spectroscopic techniques with unique sensitivity to couplings, coherence properties and real-time dynamics of a quantum system. While successfully applied to a variety of condensed phase samples, high precision experiments on isolated systems in the gas phase have been so far precluded by insufficient sensitivity. However, such experiments are essential for a precise understanding of fundamental mechanisms and to avoid misinterpretations. Here, we solve this issue by extending 2DES to isolated nanosystems in the gas phase prepared by helium nanodroplet isolation in a molecular beam-type experiment. This approach uniquely provides high flexibility in synthesizing tailored, quantum state-selected model systems of single and many-body character. In a model study of weakly-bound Rb2 and Rb3 molecules we demonstrate the method's unique capacity to elucidate interactions and dynamics in tailored quantum systems, thereby also bridging the gap to experiments in ultracold quantum science.
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Affiliation(s)
- Lukas Bruder
- Institute of Physics, University of Freiburg, 79104, Freiburg, Germany.
| | - Ulrich Bangert
- Institute of Physics, University of Freiburg, 79104, Freiburg, Germany
| | - Marcel Binz
- Institute of Physics, University of Freiburg, 79104, Freiburg, Germany
| | - Daniel Uhl
- Institute of Physics, University of Freiburg, 79104, Freiburg, Germany
| | - Romain Vexiau
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Cachan, Université Paris-Saclay, 91405, Orsay Cedex, France
| | - Nadia Bouloufa-Maafa
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Cachan, Université Paris-Saclay, 91405, Orsay Cedex, France
| | - Olivier Dulieu
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Cachan, Université Paris-Saclay, 91405, Orsay Cedex, France
| | - Frank Stienkemeier
- Institute of Physics, University of Freiburg, 79104, Freiburg, Germany.,Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Albertstr. 19, 79194, Freiburg, Germany
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11
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Messner R, Schiffmann A, Pototschnig JV, Lasserus M, Schnedlitz M, Lackner F, Ernst WE. Spectroscopy of gold atoms and gold oligomers in helium nanodroplets. J Chem Phys 2018; 149:024305. [PMID: 30007398 DOI: 10.1063/1.5026480] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The 6p 2P1/2 ← 6s 2S1/2 and 6p 2P3/2 ← 6s 2S1/2 transitions (D lines) of gold atoms embedded in superfluid helium nanodroplets have been investigated using resonant two-photon ionization spectroscopy. Both transitions are strongly blue-shifted and broadened due to the repulsive interaction between the Au valence electron and the surrounding helium. The in-droplet D lines are superimposed by the spectral signature of Au atoms relaxed into the metastable 2D states. These features are narrower than the in-droplet D lines and exhibit sharp rising edges that coincide with bare atom transitions. It is concluded that they originate from metastable 2D state AuHen exciplexes that have been ejected from the helium droplets during a relaxation process. Interestingly, the mechanism that leads to the formation of these complexes is suppressed for very large helium droplets consisting of about 2 × 106 He atoms, corresponding to a droplet diameter on the order of 50 nm. The assignment of the observed spectral features is supported by ab initio calculations employing a multiconfigurational self-consistent field method and a multi-reference configuration interaction calculation. For large helium droplets doped with Au oligomers, excitation spectra for mass channels corresponding to Aun with n = 2, 3, 4, 5, 7, and 9 are presented. The mass spectrum reveals even-odd oscillations in the number of Au atoms that constitute the oligomer, which is characteristic for coinage metal clusters. Resonances are observed close by the in-droplet D1 and D2 transitions, and the corresponding peak forms are very similar for different oligomer sizes.
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Affiliation(s)
- Roman Messner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Alexander Schiffmann
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Johann V Pototschnig
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Maximilian Lasserus
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Martin Schnedlitz
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
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12
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Lackner F, Ernst WE. Photoinduced Molecule Formation of Spatially Separated Atoms on Helium Nanodroplets. J Phys Chem Lett 2018; 9:3561-3566. [PMID: 29893573 DOI: 10.1021/acs.jpclett.8b01530] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Besides the use as cold matrix for spectroscopic studies, superfluid helium droplets have served as a cold environment for the synthesis of molecules and clusters. Since vibrational frequencies of molecules in helium droplets exhibit almost no shift compared to the free molecule values, one could assume the solvated particles move frictionless and undergo a reaction as soon as their paths cross. There have been a few unexplained observations that seemed to indicate cases of two species on one droplet not forming bonds but remaining isolated. In this work, we performed a systematic study of helium droplets doped with one rubidium and one strontium atom showing that besides a reaction to RbSr, there is a probability of finding separated Rb and Sr atoms on one droplet that only react after electronic excitation. Our results further indicate that ground-state Sr atoms can reside at the surface as well as inside the droplet.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria, European Union
| | - Wolfgang E Ernst
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria, European Union
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13
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Lackner F, Krois G, Ernst WE. Lithium atoms on helium nanodroplets: Rydberg series and ionization dynamics. J Chem Phys 2018; 147:184302. [PMID: 29141430 DOI: 10.1063/1.5004543] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The electronic excitation spectrum of lithium atoms residing on the surface of helium nanodroplets is presented and analyzed employing a Rydberg-Ritz approach. Utilizing resonant two-photon ionization spectroscopy, two different Rydberg series have been identified: one assigned to the nS(Σ) series and the other with predominantly nP(Π) character. For high Rydberg states, which have been resolved up to n = 13, the surrounding helium effectively screens the valence electron from the Li ion core, as indicated by the apparent red-shift of Li transitions and lowered quantum defects on the droplet with respect to their free atom counterparts. For low n states, the screening effect is weakened and the prevailing repulsive interaction gives rise to strongly broadened and blue-shifted transitions. The red-shifts originate from the polarization of nearby He atoms by the positive Li ion core. As a consequence of this effect, the ionization threshold is lowered by 116 ± 10 cm-1 for Li on helium droplets with a radius of about 40 Å. Upon single-photon ionization, heavy complexes corresponding to Li ions attached to intact helium droplets are detected. We conclude that ionization close to the on-droplet ionization threshold triggers a dynamic process in which the Li ion core undergoes a transition from a surface site into the droplet.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Günter Krois
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
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14
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Jasik P, Kilich T, Kozicki J, Sienkiewicz J. Potential energy surfaces of the low-lying electronic states of the Li + LiCs system. Chem Phys Lett 2018. [DOI: 10.1016/j.cplett.2018.02.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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15
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Pototschnig JV, Lackner F, Hauser AW, Ernst WE. Rydberg states of alkali atoms on superfluid helium nanodroplets: inside or outside? Phys Chem Chem Phys 2017; 19:14718-14728. [PMID: 28540939 PMCID: PMC5708348 DOI: 10.1039/c7cp02332d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 05/12/2017] [Indexed: 11/28/2022]
Abstract
Electronic excitations of an electron bound to an alkali metal ion inside a droplet of superfluid 4He are computed via a combination of helium density functional theory and the numerical integration of the Schrödinger equation for a single electron in a modified, He density dependent atomic pseudopotential. The application of a spectral method to the radial part of the valence electron wavefunction allows the computation of highly excited Rydberg states. For low principal quantum numbers, the energy required to push the electron outward is larger than the solvation energy of the ion. However, for higher principal quantum numbers the situation is reversed, which suggests the stability of a system where the ion sits inside the droplet while the valence electron orbits the nanodroplet.
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Affiliation(s)
- Johann V. Pototschnig
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Florian Lackner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Andreas W. Hauser
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Wolfgang E. Ernst
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
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16
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Hauser AW, de Lara-Castells MP. Spatial quenching of a molecular charge-transfer process in a quantum fluid: the Cs x-C 60 reaction in superfluid helium nanodroplets. Phys Chem Chem Phys 2017; 19:1342-1351. [PMID: 27975088 DOI: 10.1039/c6cp06858h] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A recent experimental study [Renzler et al., J. Chem. Phys., 2016, 145, 181101] on superfluid helium nanodroplets reported different reactivities for Cs atoms and Cs2 dimers with C60 fullerenes inside helium droplets. Alkali metal atoms and clusters are heliophobic, therefore typically residing on the droplet surface, while fullerenes are fully immersed into the droplet. In this theoretical study, which combines standard methods of computational chemistry with orbital-free helium density functional theory, we show that the experimental findings can be interpreted in the light of a quenched electron-transfer reaction between the fullerene and the alkali dopant, which is additionally hindered by a reaction barrier stemming from the necessary extrusion of helium upon approach of the two reactants.
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Affiliation(s)
- Andreas W Hauser
- Graz University of Technology, Institute of Experimental Physics, Petersgasse 16, 8010 Graz, Austria.
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17
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Cooperative Effects in Clusters and Oligonuclear Complexes of Transition Metals in Isolation. STRUCTURE AND BONDING 2016. [DOI: 10.1007/430_2016_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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18
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Abstract
As we approach the Lewis model centennial, it may be timely to discuss novel bonding motifs. Accordingly, this review discusses no-pair ferromagnetic (NPFM) bonds that hold together monovalent metallic atoms using exclusively parallel spins. Thus, without any traditional electron-pair bonds, the bonding energy per atom in these clusters can reach 20 kcal mol(-1). This review describes the origins of NPFM bonding using a valence bond (VB) analysis, which shows that this bonding motif arises from bound triplet electron pairs that are delocalized over all the close neighbors of a given atom in the cluster. The VB model accounts for the tendency of NPFM clusters to assume polyhedral shapes with rather high symmetry and for the very steep rise of the bonding energy per atom. The advent of NPFM clusters offers new horizons in chemistry of highly magnetic species sensitive to magnetic and electric fields.
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Affiliation(s)
- David Danovich
- Institute of Chemistry, The Hebrew University, 91904 Jerusalem, Israel; ,
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University, 91904 Jerusalem, Israel; ,
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19
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Pototschnig JV, Krois G, Lackner F, Ernst WE. Investigation of the RbCa molecule: Experiment and theory. JOURNAL OF MOLECULAR SPECTROSCOPY 2015; 310:126-134. [PMID: 25922550 PMCID: PMC4407902 DOI: 10.1016/j.jms.2015.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 01/12/2015] [Indexed: 06/04/2023]
Abstract
We present a thorough theoretical and experimental study of the electronic structure of RbCa. The mixed alkali-alkaline earth molecule RbCa was formed on superfluid helium nanodroplets. Excited states of the molecule in the range of 13 000-23 000 cm-1 were recorded by resonance enhanced multi-photon ionization time-of-flight spectroscopy. The experiment is accompanied by high level ab initio calculations of ground and excited state properties, utilizing a multireference configuration interaction method based on multiconfigurational self consistent field calculations. With this approach the potential energy curves and permanent electric dipole moments of 24 electronic states were calculated. In addition we computed the transition dipole moments for transitions from the ground into excited states. The combination of experiment and theory allowed the assignment of features in the recorded spectrum to the excited [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] states, where the experiment allowed to benchmark the calculation. This is the first experimental work giving insight into the previously unknown RbCa molecule, which offers great prospects in ultracold molecular physics due to its magnetic and electronic dipole moment in the [Formula: see text] ground state.
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20
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Krasnokutski SA, Huisken F. Resonant two-photon ionization spectroscopy of Al atoms and dimers solvated in helium nanodroplets. J Chem Phys 2015; 142:084311. [DOI: 10.1063/1.4908533] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Serge A. Krasnokutski
- Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena, Germany
| | - Friedrich Huisken
- Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena, Germany
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21
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Lackner F, Krois G, Buchsteiner T, Pototschnig JV, Ernst WE. Helium-droplet-assisted preparation of cold RbSr molecules. PHYSICAL REVIEW LETTERS 2014; 113:153001. [PMID: 25375707 DOI: 10.1103/physrevlett.113.153001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Indexed: 06/04/2023]
Abstract
We present a combined experimental and theoretical study of the RbSr molecule. The experimental approach is based on the formation of RbSr molecules on helium nanodroplets. Utilizing two-photon ionization spectroscopy, an excitation spectrum ranging from 11,600 up to 23,000 cm(-1) was recorded. High level ab initio calculations of potential energy curves and transition dipole moments accompany the experiment and facilitate an assignment of transitions. We show that RbSr molecules desorb from the helium droplets upon excitation, which enables dispersed fluorescence spectroscopy of free RbSr. These spectra elucidate X(2)Σ(+) ground and excited state properties. Emission spectra originating from states corresponding to the Rb(5s(2)S) + Sr(5s5p(3)P) asymptote were recorded; spin-orbit coupling was included for the simulation. The results should provide a good basis for achieving the formation of this molecule in cold collisions, thus offering intriguing prospects for ultracold molecular physics.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
| | - Günter Krois
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
| | - Thomas Buchsteiner
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
| | - Johann V Pototschnig
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
| | - Wolfgang E Ernst
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
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22
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Koch M, Kautsch A, Lackner F, Ernst WE. One- and two-color resonant photoionization spectroscopy of chromium-doped helium nanodroplets. J Phys Chem A 2014; 118:8373-9. [PMID: 24708058 PMCID: PMC4166682 DOI: 10.1021/jp501285r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
We investigate the photoinduced relaxation
dynamics of Cr atoms
embedded into superfluid helium nanodroplets. One- and two-color resonant
two-photon ionization (1CR2PI and 2CR2PI, respectively) are applied
to study the two strong ground state transitions z7P2,3,4° ←
a7S3 and y7P2,3,4° ← a7S3. Upon photoexcitation, Cr* atoms are ejected from the
droplet in various excited states, as well as paired with helium atoms
as Cr*–Hen exciplexes. For the
y7P2,3,4° intermediate state, comparison of the two methods reveals
that energetically lower states than previously identified are also
populated. With 1CR2PI we find that the population of ejected z5P3° states is reduced for increasing droplet size, indicating that population
is transferred preferentially to lower states during longer interaction
with the droplet. In the 2CR2PI spectra we find evidence for generation
of bare Cr atoms in their septet ground state (a7S3) and metastable quintet state (a5S2), which we attribute to a photoinduced fast excitation–relaxation
cycle mediated by the droplet. A fraction of Cr atoms in these ground
and metastable states is attached to helium atoms, as indicated by
blue wings next to bare atom spectral lines. These relaxation channels
provide new insight into the interaction of excited transition metal
atoms with helium nanodroplets.
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Affiliation(s)
- Markus Koch
- Institute of Experimental Physics, Graz University of Technology , Petersgasse 16, A-8010 Graz, Austria
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23
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Krois G, Lackner F, Pototschnig JV, Buchsteiner T, Ernst WE. Characterization of RbSr molecules: spectral analysis on helium droplets. Phys Chem Chem Phys 2014; 16:22373-81. [DOI: 10.1039/c4cp03135k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Ratschek M, Pototschnig JV, Hauser AW, Ernst WE. Solvation and spectral line shifts of chromium atoms in helium droplets based on a density functional theory approach. J Phys Chem A 2014; 118:6622-31. [PMID: 24906160 PMCID: PMC4141898 DOI: 10.1021/jp5034036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
![]()
The
interaction of an electronically excited, single chromium (Cr)
atom with superfluid helium nanodroplets of various size (10 to 2000
helium (He) atoms) is studied with helium density functional theory.
Solvation energies and pseudo-diatomic potential energy surfaces are
determined for Cr in its ground state as well as in the y7P, a5S, and y5P excited states. The necessary
Cr–He pair potentials are calculated by standard methods of
molecular orbital-based electronic structure theory. In its electronic
ground state the Cr atom is found to be fully submerged in the droplet.
A solvation shell structure is derived from fluctuations in the radial
helium density. Electronic excitations of an embedded Cr atom are
simulated by confronting the relaxed helium density (ρHe), obtained for Cr in the ground state, with interaction pair potentials
of excited states. The resulting energy shifts for the transitions
z7P ← a7S, y7P ← a7S, z5P ← a5S, and y5P ← a5S are compared to recent fluorescence and
photoionization experiments.
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Affiliation(s)
- Martin Ratschek
- Institute of Experimental Physics, Graz University of Technology , Petersgasse 16, A-8010 Graz, Austria
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25
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Mukherjee S, Adhikari S. The excited states of K3 cluster: The molecular symmetry adapted non-adiabatic coupling terms and diabatic Hamiltonian matrix. Chem Phys 2014. [DOI: 10.1016/j.chemphys.2014.05.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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26
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Pototschnig JV, Ratschek M, Hauser AW, Ernst WE. An ab initio study of the CrHe diatomic molecule: the effect of van der Waals distortion on a highly magnetic multi-electron system. Phys Chem Chem Phys 2014; 16:9469-78. [PMID: 24722687 DOI: 10.1039/c4cp00559g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The interaction between He and Cr is investigated by means of post-Hartree-Fock molecular orbital theory. We analyze the influence of the van der Waals forces on the complex electronic structure of the chromium atom, starting with its septet manifold and cover the first few electronically excited states up to 30 000 cm(-1). For the sake of a direct comparison with ongoing experiments on Cr-doped helium nanodroplets we extend our analysis to selected states of the quintet manifold in order to explain a non-radiating relaxation from y (7)P(o) to z (5)P(o).
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Affiliation(s)
- Johann V Pototschnig
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
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27
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Lindebner F, Kautsch A, Koch M, Ernst WE. Laser ionization and spectroscopy of Cu in superfluid helium nanodroplets. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2014; 365-366:255-259. [PMID: 25844053 PMCID: PMC4376070 DOI: 10.1016/j.ijms.2013.12.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 12/18/2013] [Accepted: 12/19/2013] [Indexed: 06/04/2023]
Abstract
Mass and optical spectroscopic methods are used for the analysis of copper (Cu) atoms and clusters doped to helium nanodroplets (HeN). A two-color resonant two-photon ionization scheme is applied to study the Cu 2P[Formula: see text]S1/2 ground state transition. The absorption is strongly broadened for Cu atoms submerged inside helium nanodroplets and a comparison with computed literature values is provided. An observed ejection of the dopant from the droplet is triggered upon excitation, populating energetically lower states. The formation of Cu n clusters up to Cu7 inside helium nanodroplets was observed by means of electron impact ionization mass spectroscopy.
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28
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Krois G, Pototschnig JV, Lackner F, Ernst WE. Spectroscopy of cold LiCa molecules formed on helium nanodroplets. J Phys Chem A 2013; 117:13719-31. [PMID: 24028555 PMCID: PMC3871282 DOI: 10.1021/jp407818k] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 09/11/2013] [Indexed: 11/30/2022]
Abstract
We report on the formation of mixed alkali-alkaline earth molecules (LiCa) on helium nanodroplets and present a comprehensive experimental and theoretical study of the ground and excited states of LiCa. Resonance enhanced multiphoton ionization time-of-flight (REMPI-TOF) spectroscopy and laser induced fluorescence (LIF) spectroscopy were used for the experimental investigation of LiCa from 15000 to 25500 cm(-1). The 4(2)Σ(+) and 3(2)Π states show a vibrational structure accompanied by distinct phonon wings, which allows us to determine molecular parameters as well as to study the interaction of the molecule with the helium droplet. Higher excited states (4(2)Π, 5(2)Σ(+), 5(2)Π, and 6(2)Σ(+)) are not vibrationally resolved and vibronic transitions start to overlap. The experimental spectrum is well reproduced by high-level ab initio calculations. By using a multireference configuration interaction (MRCI) approach, we calculated the 19 lowest lying potential energy curves (PECs) of the LiCa molecule. On the basis of these calculations, we could identify previously unobserved transitions. Our results demonstrate that the helium droplet isolation approach is a powerful method for the characterization of tailor-made alkali-alkaline earth molecules. In this way, important contributions can be made to the search for optimal pathways toward the creation of ultracold alkali-alkaline earth ground state molecules from the corresponding atomic species. Furthermore, a test for PECs calculated by ab initio methods is provided.
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Affiliation(s)
- Günter Krois
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Johann V. Pototschnig
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Wolfgang E. Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
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29
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Yang S, Ellis AM, Spence D, Feng C, Boatwright A, Latimer E, Binns C. Growing metal nanoparticles in superfluid helium. NANOSCALE 2013; 5:11545-11553. [PMID: 24107922 DOI: 10.1039/c3nr04003h] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Helium droplets provide a cold and confined environment where atomic and/or molecular dopants can aggregate into clusters and nanoparticles. In particular, the sequential addition of different materials to helium droplets can lead to the formation of a wide range of nanoparticles, including core-shell nanoparticles, which can then be deposited onto a surface. Here we briefly discuss the fundamental properties of helium droplets and then address their implications for the formation of clusters and nanoparticles. Several key experiments on atomic and molecular clusters will be highlighted and new results obtained for nanoparticles formed in this way will be presented. Finally, the versatility, the limitations and new possibilities provided by superfluid helium droplets in nanoscience and nanotechnology will be addressed.
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Affiliation(s)
- Shengfu Yang
- Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK.
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30
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Poms J, Hauser AW, Ernst WE. Helium nanodroplets doped with xenon and rubidium atoms: a case study of van der Waals interactions between heliophilic and heliophobic dopants. Phys Chem Chem Phys 2012; 14:15158-65. [DOI: 10.1039/c2cp42333b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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31
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Giese C, Stienkemeier F, Mudrich M, Hauser AW, Ernst WE. Homo- and heteronuclear alkali metal trimers formed on helium nanodroplets. Part II. Femtosecond spectroscopy and spectra assignments. Phys Chem Chem Phys 2011; 13:18769-80. [PMID: 21869967 DOI: 10.1039/c1cp21191a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Homo- and heteronuclear alkali quartet trimers of type K(3-n)Rb(n) (n = 0,1,2,3) formed on helium nanodroplets are probed by one-color femtosecond (fs) photoionization (PI) spectroscopy. The obtained frequencies are assigned to vibrations in different electronic states in comparison to high level ab initio calculations of the involved potentials including pronounced Jahn-Teller and spin-orbit couplings. Despite the fact that the resulting complex vibronic structure of the heavy alkali molecules complicates the comparison of experiment and theory we find good agreement for many of the observed lines for all species.
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Affiliation(s)
- Christian Giese
- Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany.
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32
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Hauser AW, Ernst WE. Homo- and heteronuclear alkali metal trimers formed on helium nanodroplets. Part I. Vibronic spectra simulations based on ab initio calculations. Phys Chem Chem Phys 2011; 13:18762-8. [DOI: 10.1039/c1cp21163c] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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33
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Koch M, Callegari C, Ernst WE. Alkali-metal electron spin density shift induced by a helium nanodroplet. Mol Phys 2010. [DOI: 10.1080/00268971003623401] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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34
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Koch M, Auböck G, Callegari C, Ernst WE. Coherent spin manipulation and ESR on superfluid helium nanodroplets. PHYSICAL REVIEW LETTERS 2009; 103:035302. [PMID: 19659290 DOI: 10.1103/physrevlett.103.035302] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 06/13/2009] [Indexed: 05/28/2023]
Abstract
Superfluid helium nanodroplets provide a versatile substrate to cool atoms and molecules, and to assemble weakly bound complexes. Absence of spin-relaxation mechanisms makes He nanodroplets ideal to isolate open-shell atoms and create a spin-polarized system. Here, we show the first coherent manipulation of such a system by resonant excitation of a magnetic-dipole transition. Observation of approximately 50 Rabi oscillations demonstrates coherent population transfer with minimal dephasing. Ours is also the first application of ESR spectroscopy to doped He nanodroplets. This unique environment results in extremely sharp lines and hyperfine-resolved spectra: those of single 39K and 85Rb dopant atoms presented here denote an increase of the Fermi contact interaction, which we can follow as a function of droplet size, reflecting the distortion of the valence-electron wave function due to the surrounding He.
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Affiliation(s)
- Markus Koch
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
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35
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Leino M, Viel A, Zillich RE. Electronically excited rubidium atom in a helium cluster or film. J Chem Phys 2008; 129:184308. [DOI: 10.1063/1.3009279] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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36
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Auböck G, Nagl J, Callegari C, Ernst WE. Observation of relativistic E⊗e vibronic coupling in Rb3 and K3 quartet states on helium droplets. J Chem Phys 2008; 129:114501. [DOI: 10.1063/1.2976765] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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37
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Hauser AW, Callegari C, Soldán P, Ernst WE. On the doublet states of the potassium trimer. J Chem Phys 2008; 129:044307. [PMID: 18681646 DOI: 10.1063/1.2956492] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The potassium trimer is investigated in its lowest electronic doublet states, employing several high-level ab initio methods (coupled cluster with single, double, and noniterative triple excitations, multiconfiguration self-consistent field, and multireference Rayleigh-Schrodinger perturbation theory of second order). One-dimensional cuts through the lowest 12 electronic states at C(2v) symmetry give insight in the complex electronic structure of the trimer, showing several (pseudo-)Jahn-Teller distortions that involve two or three excited states. Contour plots of the involved molecular orbitals are shown to prove the validity of the shell model frequently used for a qualitative description of metallic clusters.
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Affiliation(s)
- Andreas W Hauser
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
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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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