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Reider AM, Mayerhofer J, Martini P, Scheier P, Lushchikova OV. Mixed Cluster Ions of Magnesium and C 60. J Phys Chem A 2024; 128:848-857. [PMID: 38272839 PMCID: PMC10860146 DOI: 10.1021/acs.jpca.3c06902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 01/13/2024] [Accepted: 01/15/2024] [Indexed: 01/27/2024]
Abstract
Magnesium clusters exhibit a pronounced nonmetal-to-metal transition, and the neutral dimer is exceptionally weakly bound. In the present study, we formed pristine Mgnz+ (n = 1-100, z = 1-3) clusters and mixed (C60)mMgnz+ clusters (m = 1-7, z = 1, 2) upon electron irradiation of neutral helium nanodroplets doped with magnesium or a combination of C60 and magnesium. The mass spectra obtained for pristine magnesium cluster ions exhibit anomalies, consistent with previous reports in the literature. The anomalies observed for C60Mgn+ strongly suggest that Mg atoms tend to wet the surface of the single fullerene positioning itself above the center of a pentagonal or hexagonal face, while, for (C60)mMgnz+, the preference for Mg to position itself within the dimples formed by fullerene cages becomes apparent. Besides doubly charged cluster ions, with the smallest member Mg22+, we also observed the formation of triply charged ions Mgn3+ with n > 24. The ion efficiency curves of singly and multiply charged ions exhibit pronounced differences compared to singly charged ions at higher electron energies. These findings indicate that sequential Penning ionization is essential in the formation of doubly and triply charged ions inside doped helium nanodroplets.
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Affiliation(s)
- Anna Maria Reider
- Institut
für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Jan Mayerhofer
- Institut
für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - Paul Martini
- 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
| | - Olga V. Lushchikova
- Institut
für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
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2
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Fielicke A. Probing the binding and activation of small molecules by gas-phase transition metal clusters via IR spectroscopy. Chem Soc Rev 2023. [PMID: 37162518 DOI: 10.1039/d2cs00104g] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Isolated transition metal clusters have been established as useful models for extended metal surfaces or deposited metal particles, to improve the understanding of their surface chemistry and of catalytic reactions. For this objective, an important milestone has been the development of experimental methods for the size-specific structural characterization of clusters and cluster complexes in the gas phase. This review focusses on the characterization of molecular ligands, their binding and activation by small transition metal clusters, using cluster-size specific infrared action spectroscopy. A comprehensive overview and a critical discussion of the experimental data available to date is provided, reaching from the initial results obtained using line-tuneable CO2 lasers to present-day studies applying infrared free electron lasers as well as other intense and broadly tuneable IR laser sources.
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Affiliation(s)
- André Fielicke
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany.
- Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623 Berlin, Germany
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3
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Jiang Y, Lv J, He W, Peng P. Lowest-energy structural and electronic properties of Cu Zr13− (n = 3–10) clusters in metallic glasses via CALYPSO search and density functional theory calculations. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.117603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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4
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Brieuc F, Schran C, Uhl F, Forbert H, Marx D. Converged quantum simulations of reactive solutes in superfluid helium: The Bochum perspective. J Chem Phys 2020; 152:210901. [DOI: 10.1063/5.0008309] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Affiliation(s)
- Fabien Brieuc
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Christoph Schran
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Felix Uhl
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Harald Forbert
- Center for Solvation Science ZEMOS, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Dominik Marx
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
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5
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Hapka M, Rajchel Ł, Modrzejewski M, Schäffer R, Chałasiński G, Szczęśniak MM. The nature of three-body interactions in DFT: Exchange and polarization effects. J Chem Phys 2017; 147:084106. [PMID: 28863509 DOI: 10.1063/1.4986291] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We propose a physically motivated decomposition of density functional theory (DFT) 3-body nonadditive interaction energies into the exchange and density-deformation (polarization) components. The exchange component represents the effect of the Pauli exclusion in the wave function of the trimer and is found to be challenging for density functional approximations (DFAs). The remaining density-deformation nonadditivity is less dependent upon the DFAs. Numerical demonstration is carried out for rare gas atom trimers, Ar2-HX (X = F, Cl) complexes, and small hydrogen-bonded and van der Waals molecular systems. None of the tested semilocal, hybrid, and range-separated DFAs properly accounts for the nonadditive exchange in dispersion-bonded trimers. By contrast, for hydrogen-bonded systems, range-separated DFAs achieve a qualitative agreement to within 20% of the reference exchange energy. A reliable performance for all systems is obtained only when the monomers interact through the Hartree-Fock potential in the dispersion-free Pauli blockade scheme. Additionally, we identify the nonadditive second-order exchange-dispersion energy as an important but overlooked contribution in force-field-like dispersion corrections. Our results suggest that range-separated functionals do not include this component, although semilocal and global hybrid DFAs appear to imitate it in the short range.
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Affiliation(s)
- Michał Hapka
- Faculty of Chemistry, University of Warsaw, ul. L. Pasteura 1, 02-093 Warsaw, Poland
| | - Łukasz Rajchel
- Faculty of Chemistry, University of Duisburg-Essen, Universitätsstraße 5, 45117 Essen, Germany
| | - Marcin Modrzejewski
- Faculty of Chemistry, University of Warsaw, ul. L. Pasteura 1, 02-093 Warsaw, Poland
| | - Rainer Schäffer
- Faculty of Chemistry, University of Duisburg-Essen, Universitätsstraße 5, 45117 Essen, Germany
| | - Grzegorz Chałasiński
- Faculty of Chemistry, University of Warsaw, ul. L. Pasteura 1, 02-093 Warsaw, Poland
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6
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Zhang X, Brauer NB, Berden G, Rijs AM, Drabbels M. Mid-infrared spectroscopy of molecular ions in helium nanodroplets. J Chem Phys 2012; 136:044305. [DOI: 10.1063/1.3678011] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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7
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Liang T, Flynn SD, Morrison AM, Douberly GE. Quantum Cascade Laser Spectroscopy and Photoinduced Chemistry of Al–(CO)n Clusters in Helium Nanodroplets. J Phys Chem A 2011; 115:7437-47. [DOI: 10.1021/jp203367t] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tao Liang
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Steven D. Flynn
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Alexander M. Morrison
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Gary E. Douberly
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
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8
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Orr BJ. Spectroscopy and energetics of the acetylene molecule: dynamical complexity alongside structural simplicity. INT REV PHYS CHEM 2010. [DOI: 10.1080/01442350600892577] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Brian J. Orr
- a Department of Physics and Centre for Lasers and Applications , Macquarie University , Sydney , NSW 2109 , Australia
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9
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Smolarek S, Brauer NB, Buma WJ, Drabbels M. IR Spectroscopy of Molecular Ions by Nonthermal Ion Ejection from Helium Nanodroplets. J Am Chem Soc 2010; 132:14086-91. [DOI: 10.1021/ja1034655] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Szymon Smolarek
- University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands, and Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Nils B. Brauer
- University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands, and Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Wybren J. Buma
- University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands, and Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Marcel Drabbels
- University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands, and Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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10
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Falconer TM, Lewis WK, Bemish RJ, Miller RE, Glish GL. Formation of cold ion-neutral clusters using superfluid helium nanodroplets. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:054101. [PMID: 20515155 DOI: 10.1063/1.3386584] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A strategy for forming and detecting cold ion-neutral clusters using superfluid helium nanodroplets is described. Sodium cations generated via thermionic emission are directed toward a beam of helium droplets that can also pick up neutral molecules and form a cluster with the captured Na(+). The composition of the clusters is determined by mass spectrometric analysis following a desolvation step. It is shown that the polar molecules H(2)O and HCN are picked up and form ion-neutral clusters with sizes and relative abundances that are in good agreement with those predicted by the statistics used to describe neutral cluster formation in helium droplets. [Na(H(2)O)(n)](+) clusters containing six to 43 water molecules were observed, a size range of sodiated water clusters difficult to access in the gas phase. Clusters containing N(2) were in lower abundance than expected, suggesting that the desolvation process heats the clusters sufficiently to dissociate those containing nonpolar molecules.
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Affiliation(s)
- Travis M Falconer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA
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11
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Min AR, Lee SJ, Choi MY, Miller RE. Electric Field Dependence Experiments and ab Initio Calculations of Three Cytosine Tautomers in Superfluid Helium Nanodroplets. B KOREAN CHEM SOC 2009. [DOI: 10.5012/bkcs.2009.30.12.3039] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Gamboa A, Hernández H, Ramilowski JA, Losada JC, Benito RM, Borondo F, Farrelly D. Chaos in the classical mechanics of bound and quasi-bound HX-4He complexes with X = F, Cl, Br, CN. Phys Chem Chem Phys 2009; 11:8203-13. [PMID: 19756276 DOI: 10.1039/b902486g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The classical dynamics of weakly bound floppy van der Waals complexes have been extensively studied in the past except for the weakest of all, i.e., those involving He atoms. These complexes are of considerable current interest in light of recent experimental work focussed on the study of molecules trapped in small droplets of the quantum solvent (4)He. Despite a number of quantum investigations, details on the dynamics of how quantum solvation occurs remain unclear. In this paper, the classical rotational dynamics of a series of van der Waals complexes, HX-(4)He with X = F, Cl, Br, CN, are studied. In all cases, the ground state dynamics are found to be almost entirely chaotic, in sharp contrast to other floppy complexes, such as HCl-Ar, for which chaos sets in only at relatively high energies. The consequences of this result for quantum solvation are discussed. We also investigate rotationally excited states with J = 1 which, except for HCN-(4)He, are actually resonances that decay by rotational pre-dissociation.
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Affiliation(s)
- Antonio Gamboa
- Grupo de Sistemas Complejos, Departamento de Física y Mecánica, Escuela Técnica Superior de Ingenieros Agrónomos, Universidad Politécnica de Madrid, 28040 Madrid, Spain
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13
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Choi MY, Miller RE. Imidazole dimer and its water complexes formed in superfluid helium nanodroplets: Infrared spectroscopic studies of free OH vibrational stretching modes. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.07.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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14
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Snyder DN, Szczęśniak MM, Chałasiński G. The nature of interactions between clusters of Mg and Zn with HCN from symmetry-adapted perturbation theory based of DFT. J Chem Phys 2009; 130:224704. [DOI: 10.1063/1.3152122] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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15
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Stiles PL, Douberly GE, Miller RE. High-resolution infrared spectroscopy of Mg-HF and Mg-(HF)2 solvated in helium nanodroplets. J Chem Phys 2009; 130:184313. [PMID: 19449927 DOI: 10.1063/1.3137122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
High-resolution infrared (IR) spectroscopy is used to investigate the Mg-HF and Mg-(HF)(2) van der Waals complexes. Both complexes are formed and probed within helium nanodroplets. Rotationally resolved zero-field and Stark spectra are assigned to a linear binary complex composed of a Mg atom bound to the hydrogen end of the HF molecule. Although high level ab initio calculations predict a fluorine bonded complex, none of the observed IR bands can be assigned to this complex. The collocation method is employed to determine the bound states on the two-dimensional intermolecular Mg-HF potential energy surface. The ground and first excited state wave functions for this potential surface have zero amplitude in the well corresponding to the fluorine bonded complex, consistent with experiment. The two HF stretching bands of the Mg-(HF)(2) complex are observed and assigned using a combination of the spectral symmetry, ab initio calculations, pick-up cell pressure dependencies, and dipole moment measurements. Comparisons with the helium solvated HF dimer show large changes to the HF stretching frequencies upon the addition of a single Mg atom to the hydrogen side of (HF)(2).
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Affiliation(s)
- Paul L Stiles
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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16
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Panteleev SV, Ignatov SK, Maslennikov SV. Adsorption of solvent and oxidant molecules on magnesium surface: effect on the electronic structure and reactivity of magnesium in reactions of Grignard reagent formation. Russ Chem Bull 2009. [DOI: 10.1007/s11172-008-0074-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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17
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Kłos J, Żuchowski PS, Rajchel Ł, Chałasiński G, Szczęśniak MM. Nonadditive interactions in ns2 and spin-polarized ns metal atom trimers. J Chem Phys 2008; 129:134302. [DOI: 10.1063/1.2982801] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Choi MY, Dong F, Han SW, Miller RE. Nonplanarity of Adenine: Vibrational Transition Moment Angle Studies in Helium Nanodroplets. J Phys Chem A 2008; 112:7185-90. [DOI: 10.1021/jp8012688] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Myong Yong Choi
- Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 660-701, Korea, and Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Feng Dong
- Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 660-701, Korea, and Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Sang Woo Han
- Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 660-701, Korea, and Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Roger E. Miller
- Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 660-701, Korea, and Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
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19
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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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20
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Douberly GE, Miller RE. Rotational Dynamics of HCN−M (M = Na, K, Rb, Cs) van der Waals Complexes Formed on the Surface of Helium Nanodroplets. J Phys Chem A 2007; 111:7292-302. [PMID: 17602450 DOI: 10.1021/jp070042a] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Infrared laser spectroscopy was used to probe the unique rotational dynamics of the HCN-M (M = Na, K, Rb, Cs) complexes formed on the surface of helium droplets. The nu1 CH stretch ro-vibrational spectra were measured revealing what appears to be the P and R contours of a nearly rigid linear rotor. To simulate the linear molecule spectra, given a rotational temperature of 0.37 K, effective moments of inertia, IB, were required to be 10(4)-10(5) amu.A2 larger than the ab initio predicted values. The large moments of inertia were found to be strongly dependent on both the mass of the complex and the size of the helium droplet, consistent with a model where the dopant is located in a dimple site on the surface of the droplet. In this model, the moment of inertia is representative of the rotational motion of the dopant on the surface about an inertial axis through the center of the droplet.
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Affiliation(s)
- Gary E Douberly
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
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21
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Auböck G, Nagl J, Callegari C, Ernst WE. Triplet State Excitation of Alkali Molecules on Helium Droplets: Experiments and Theory. J Phys Chem A 2007; 111:7404-10. [PMID: 17552501 DOI: 10.1021/jp070891y] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this paper, we discuss the electronic structure of alkali dimer molecules in 3Pig states on the surface of a helium droplet. The perturbation due to the droplet will in general not satisfy rotational symmetry around the internuclear axis of the diatom and thus, in addition to a broadening and blue shift, will cause a splitting of electronic levels that are degenerate in the free molecules. We propose a model based on general symmetry arguments and on a small number of physically reasonable parameters. We demonstrate that such a model accounts for the essential features of laser-induced fluorescence (LIF) and magnetic circular dichroism (MCD) spectra of the (1)3Pig-a3Sigma+ transition of Rb2 and K2. Furthermore the MCD spectra, analyzed according to the approach of Langford and Williamson [J. Phys. Chem. A 1998, 102, 2415], allow a determination of the populations of Zeeman sublevels in the ground state and thus a measurement of the surface temperature of the droplet. The latter agrees with the accepted temperature, 0.37 K, measured in the interior of a droplet.
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Affiliation(s)
- Gerald Auböck
- Institute of Experimental Physics, TU Graz, Petersgasse 16, 8010 Graz, Austria, EU
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22
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Stiles PL, Miller RE. High-Resolution Infrared Spectroscopy of HCN−Agn (n = 1−4) Complexes Solvated in Superfluid Helium Droplets. J Phys Chem A 2007; 111:7382-90. [PMID: 17518451 DOI: 10.1021/jp0707945] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
High-resolution infrared spectroscopy has been used to determine the structures, C-H stretching frequencies, and dipole moments of the HCN-Agn (n = 1-3) complexes formed in superfluid helium droplets. The HCN-Ag4 cluster was tentatively assigned based upon pick-up cell pressure dependencies and harmonic vibrational shift calculations. Ab initio and density functional theory calculations were used in conjunction with the high-resolution spectra to analyze the bonding nature of each cluster. All monoligated species reported here are bound through the nitrogen end of the HCN molecule. The HCN-Agn complexes are structurally similar to the previously reported HCN-Cun clusters, with the exception of the HCN-Ag binary complex. Although the interaction between the HCN and the Agn clusters follows the same trends as the HCN-Cun clusters, the more diffuse nature of the electrons surrounding the silver atoms results in a much weaker interaction.
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Affiliation(s)
- Paul L Stiles
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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23
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Douberly GE, Merritt JM, Miller RE. Infrared−Infrared Double Resonance Spectroscopy of the Isomers of Acetylene−HCN and Cyanoacetylene−HCN in Helium Nanodroplets. J Phys Chem A 2007; 111:7282-91. [PMID: 17465533 DOI: 10.1021/jp070015k] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Infrared-infrared double resonance spectroscopy is used to probe the vibrational dynamics of molecular complexes solvated in helium nanodroplets. We report results for the acetylene-HCN and cyanoacetylene-HCN binary complexes, each having two stable isomers. We find that vibrational excitation of an acetylene-HCN complex results in a population transfer to the other isomer. Photoinduced isomerization is found to be dependent on both the initially excited vibrational mode and the identity of the acetylene-HCN isomer. However, population transfer is not observed for the cyanoacetylene-HCN complexes. The results are rationalized in terms of the ab initio intermolecular potential energy surfaces for the two systems with particular emphasis on the long-range barriers to rearrangement.
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Affiliation(s)
- Gary E Douberly
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
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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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25
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Choi MY, Miller RE. Infrared Laser Spectroscopy of Uracil and Thymine in Helium Nanodroplets: Vibrational Transition Moment Angle Study. J Phys Chem A 2007; 111:2475-9. [PMID: 17388352 DOI: 10.1021/jp0674625] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vibrational spectra are reported in the N-H stretching region for uracil and thymine monomers in helium nanodroplets. Each monomer shows only a single isomer, the global minimum, in agreement with previous experimental and theoretical studies. The assignment of the infrared vibrational bands in the spectra is aided by the measurement of the corresponding vibrational transition moment angles (VTMAs) and ab initio frequency calculations. The ambiguity in the VTMA assignment of the N3H band for the uracil monomer is explained by the presence of dimer bands, which are overlapped with the monomer band.
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Affiliation(s)
- Myong Yong Choi
- Department of Chemistry, The University of North Carolina at Chapel Hill, North Carolina 27599, USA.
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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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Asmis KR, Fielicke A, von Helden G, Meijer G. Chapter 8 Vibrational spectroscopy of gas-phase clusters and complexes. ATOMIC CLUSTERS: FROM GAS PHASE TO DEPOSITED 2007. [DOI: 10.1016/s1571-0785(07)12008-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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28
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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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29
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Choi MY, Miller RE. Infrared Laser Spectroscopy of Imidazole Complexes in Helium Nanodroplets: Monomer, Dimer, and Binary Water Complexes. J Phys Chem A 2006; 110:9344-51. [PMID: 16869682 DOI: 10.1021/jp0624146] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Infrared laser spectroscopy has been used to characterize imidazole (IM), imidazole dimer (IMD), and imidazole-water (IMW) binary systems formed in helium nanodroplets. The experimental results are compared with ab initio calculations reported here. Vibrational transition moment angles provide conclusive assignments for the various complexes studied here, including IM, one isomer of IMD, and two isomers of the IMW binary complexes.
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Affiliation(s)
- Myong Yong Choi
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
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30
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Mikosz AA, Ramilowski JA, Farrelly D. Quantum solvation dynamics of HCN in a helium-4 droplet. J Chem Phys 2006; 125:014312. [PMID: 16863303 DOI: 10.1063/1.2213253] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Ultracold nanodroplets of helium-4, containing several thousands of He atoms, offer considerable promise as microscopic cryogenic chambers. Potential applications include the creation of tailor-made chemical or biomolecular complexes and studies of superfluidity in nanoscale systems. Recent experiments have succeeded in interrogating droplets of quantum solvent which consist of as few as 1-20 helium-4 atoms and which contain a single solute molecule. This allows the transition from a floppy, but essentially molecular, complex to a dissolved molecule to be followed and, surprisingly, the transition is found to occur quite rapidly, in some cases for as few as N = 7-20 solvent atoms. For example, in experiments on helium-4 droplets seeded with CO molecules [Tang and McKellar, J. Chem. Phys. 119, 754 (2003)], two series of transitions are observed which correlate with the a-type (Delta K = 0) and b-type (Delta K = +/-1) lines of the binary complex, CO-He (K is the quantum number associated with the projection of the total angular momentum onto the vector connecting the atom and the molecular center of mass). The a-type series, which evolves from the end-over-end rotational motion of the CO-He binary complex, saturates to the nanodroplet limit for as few as 10-15 helium-4 atoms, i.e., the effective moment of inertia of the molecule converges to its asymptotic (solvated) value quite rapidly. In contrast, the b-type series, which evolves from the free-molecule rotational mode, disappears altogether for N approximately 7 atoms. Similar behavior is observed in recent computational studies of HCN(4He)N droplets [Paolini et al., J. Chem. Phys. 123, 114306 (2005)]. In this article the quantum solvation of HCN in small helium-4 droplets is studied using a new fixed-node diffusion Monte Carlo (DMC) procedure. In this approach a Born-Oppenheimer-type separation of radial and angular motions is introduced as a means of computing nodal surfaces of the many-body wave functions which are required in the fixed-node DMC method. Excited rotational energies are calculated for HCN(4He)N droplets with N = 1-20: the adiabatic node approach also allows concrete physical mechanisms to be proposed for the predicted disappearance of the b-type series as well as the rapid convergence of the a-type series to the nanodroplet limit with increasing N. The behavior of the a-type series is traced directly to the mechanics of angular momentum coupling-and decoupling-between identical bosons and the molecular rotor. For very small values of N there exists significant angular momentum coupling between the molecule and the helium atoms: at N approximately 10 solvation appears to be complete as evidenced by significant decoupling of the molecule and solvent angular momenta. The vanishing of the b-type series is predicted to be a result of increasing He-He repulsion as the number of solvent atoms increases.
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Affiliation(s)
- Aleksandra A Mikosz
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA
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31
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Choi MY, Miller RE. Four Tautomers of Isolated Guanine from Infrared Laser Spectroscopy in Helium Nanodroplets. J Am Chem Soc 2006; 128:7320-8. [PMID: 16734487 DOI: 10.1021/ja060741l] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Infrared laser spectroscopy is used to study the four lowest energy tautomers of guanine, isolated in helium nanodroplets. The large number of vibrational bands observed in the infrared spectrum are assigned by comparing the corresponding experimental vibrational transition moment angles with those obtained from ab initio theory. The result is the conclusive assignment of the spectrum to the N9H-Keto, N7H-Keto, N9Ha-Enol(trans), and N9Hb-Enol(cis) tautomers. The dipole moments of these tautomers are also experimentally determined and compared with ab initio theory.
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Affiliation(s)
- Myong Yong Choi
- Department of Chemistry, The University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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32
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Roger E. Miller: Publications. INT REV PHYS CHEM 2006. [DOI: 10.1080/01442350600709243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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33
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Choi MY, Douberly GE, Falconer TM, Lewis WK, Lindsay CM, Merritt JM, Stiles PL, Miller RE. Infrared spectroscopy of helium nanodroplets: novel methods for physics and chemistry. INT REV PHYS CHEM 2006. [DOI: 10.1080/01442350600625092] [Citation(s) in RCA: 327] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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34
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Lewis WK, Bemish RJ, Miller RE. Fragmentation of HCN in optically selected mass spectrometry: Nonthermal ion cooling in helium nanodroplets. J Chem Phys 2005; 123:141103. [PMID: 16238367 DOI: 10.1063/1.2046672] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
A technique that combines infrared laser spectroscopy and helium nanodroplet mass spectrometry, which we refer to as optically selected mass spectrometry, is used to study the efficiency of ion cooling in helium. Electron-impact ionization is used to form He(+) ions within the droplets, which go on to transfer their charge to the HCN dopant molecules. Depending upon the droplet size, the newly formed ion either fragments or is cooled by the helium before fragmentation can occur. Comparisons with gas-phase fragmentation data suggest that the cooling provided by the helium is highly nonthermal. An "explosive" model is proposed for the cooling process, given that the initially hot ion is embedded in such a cold solvent.
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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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35
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Lewis WK, Lindsay CM, Bemish RJ, Miller RE. Probing charge-transfer processes in helium nanodroplets by optically selected mass spectrometry (OSMS): charge steering by long-range interactions. J Am Chem Soc 2005; 127:7235-42. [PMID: 15884965 DOI: 10.1021/ja042489s] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electron impact ionization of a helium atom in a helium nanodroplet is followed by rapid charge migration, which can ultimately result in the localization of the charge on an atomic or molecular solute. This process is studied here for the cases of hydrogen cyanide, acetylene, and cyanoacetylene in helium, using a new experimental method we call optically selected mass spectrometry (OSMS). The method combines infrared laser spectroscopy with mass spectrometry to separate the contributions to the overall droplet beam mass spectrum from the various species present under a given set of conditions. This is done by vibrationally exciting a specific species that exists in a subset of the droplets (for example, the droplets containing a single HCN molecule). The resulting helium evaporation leads to a concomitant reduction in the ionization cross sections for these droplets. This method is used to study the charge migration in helium and reveals that the probability of charge transfer to a solvated molecule does not approach unity for small droplets and depends on the identity of the solvated molecule. The experimental results are explained quantitatively by considering the effect of the electrostatic potential (between the charge and the embedded molecule) on the trajectory of the migrating charge.
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Affiliation(s)
- William K Lewis
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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36
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Xu * Y, Wijngaarden JV, Jäger * W. Microwave spectroscopy of ternary and quaternary van der Waals clusters. INT REV PHYS CHEM 2005. [DOI: 10.1080/01442350500252039] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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37
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Choi MY, Dong F, Miller RE. Multiple tautomers of cytosine identified and characterized by infrared laser spectroscopy in helium nanodroplets: probing structure using vibrational transition moment angles. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2005; 363:393-413. [PMID: 15664890 DOI: 10.1098/rsta.2004.1499] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Infrared laser spectroscopy in helium nanodroplets is used to identify and characterize several distinct tautomers of cytosine. The experimentally observed species correspond to the lowest-energy structures obtained from ab initio calculations, also reported here. The assignment of the infrared vibrational bands in the spectra is aided by the measurement of the corresponding vibrational transition moment angles, which are also calculated using ab initio methods. In the present study we confirm the existence of three primary tautomers and provide tentative assignments for even higher-energy forms of cytosine in helium nanodroplets.
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Affiliation(s)
- M Y Choi
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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38
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Choi MY, Miller RE. Multiple isomers of uracil–water complexes: infrared spectroscopy in helium nanodroplets. Phys Chem Chem Phys 2005; 7:3565-73. [PMID: 16294232 DOI: 10.1039/b507100c] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Infrared laser spectroscopy is used to show that four structural isomers of the uracil-water binary complex are formed in helium nanodroplets. The assignment of the infrared spectra is aided by measurements of vibrational transition moment angles (VTMAs) for various vibrational modes of these complexes. The experimental results are in excellent agreement with ab initio calculations, which had previously predicated the existence of the same four isomers. The results suggest that the relative abundances of the various isomers formed in helium droplets have more to do with the widths of the valleys in the potential surface that funnel into a particular local minimum than on the associated energetics.
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Affiliation(s)
- M Y Choi
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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39
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Douberly GE, Merritt JM, Miller RE. IR–IR double resonance spectroscopy in helium nanodroplets: Photo-induced isomerization. Phys Chem Chem Phys 2005. [DOI: 10.1039/b417553k] [Citation(s) in RCA: 30] [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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40
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Moore DT, Miller RE. Structure of the Acetylene−Magnesium Binary Complex from Infrared Laser Spectroscopy in Helium Nanodroplets. J Phys Chem A 2004. [DOI: 10.1021/jp0403238] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- D. T. Moore
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599
| | - R. E. Miller
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599
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41
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Stiles PL, Moore DT, Miller RE. Structures of HCN-Mgn (n=2–6) complexes from rotationally resolved vibrational spectroscopy andab initiotheory. J Chem Phys 2004; 121:3130-42. [PMID: 15291623 DOI: 10.1063/1.1768932] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
High-resolution infrared laser spectroscopy has been used to determine the structures of HCN-Mgn complexes formed in helium nanodroplets. The magnesium atoms are first added to the droplets to ensure that the magnesium complexes are preformed before the HCN molecule is added. The vibrational frequencies, structures, and dipole moments of these complexes are found to vary dramatically with cluster size, illustrating the nonadditive nature of the HCN-magnesium interactions. All of the complexes discussed here have the nitrogen end of the HCN pointing towards the magnesium clusters. For Mg3, the HCN binds to the "threefold" site, yielding a symmetric top spectrum. Although the HCN-Mg4 complex also has C3v symmetry, the HCN sits "on-top" of a single magnesium atom. These structures are confirmed by both ab initio calculations and measurements of the dipole moments. Significant charge transfer is observed in the case of HCN-Mg4, indicative of charge donation from the lone pair on the nitrogen of HCN into the lowest unoccupied molecular orbital of the Mg4.
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Affiliation(s)
- P L Stiles
- Department of Chemistry, University of North Carolina, Chapel Hill 27599, USA
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42
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Merritt JM, Douberly GE, Miller RE. Infrared–infrared double resonance spectroscopy of cyanoacetylene in helium nanodroplets. J Chem Phys 2004; 121:1309-16. [PMID: 15260673 DOI: 10.1063/1.1763147] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Infrared-infrared double resonance spectroscopy is used as a probe of the vibrational dynamics of cyanoacetylene in helium droplets. The nu1 C-H stretching vibration of cyanoacetylene is excited by an infrared laser and subsequent vibrational relaxation results in the evaporation of approximately 660 helium atoms from the droplet. A second probe laser is then used to excite the same C-H stretching vibration downstream of the pump, corresponding to a time delay of approximately 175 micros. The hole burned by the pump laser is narrower than the single resonance spectrum, owing to the fact that the latter is inhomogeneously broadened by the droplet size distribution. The line width of the hole is characteristic of another broadening source that depends strongly on droplet size.
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Affiliation(s)
- J M Merritt
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599
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43
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Dong F, Miller RE. Laser Spectroscopy of Cyanoacetylene−Mgn Complexes in Helium Nanodroplets: Multiple Isomers. J Phys Chem A 2004. [DOI: 10.1021/jp031194i] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- F. Dong
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599
| | - R. E. Miller
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599
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44
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Kwon Y, Whaley KB. Microscopic two-fluid theory of rotational constants of the OCS–H2 complex in 4He droplets. J Chem Phys 2003. [DOI: 10.1063/1.1582850] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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45
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Stiles PL, Moore DT, Miller RE. Infrared spectroscopy of the isomers of magnesium–HCN formed in helium nanodroplets: Comparisons with ab initio calculations. J Chem Phys 2003. [DOI: 10.1063/1.1562160] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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46
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Stiles PL, Nauta K, Miller RE. Dipole moments of molecules solvated in helium nanodroplets. PHYSICAL REVIEW LETTERS 2003; 90:135301. [PMID: 12689300 DOI: 10.1103/physrevlett.90.135301] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2002] [Indexed: 05/24/2023]
Abstract
Stark spectra are reported for hydrogen cyanide and cyanoacetylene solvated in helium nanodroplets. The goal of this study is to understand the influence of the helium solvent on measurements of the permanent electric dipole moment of a molecule. We find that the dipole moments of the helium solvated molecules, calculated assuming the electric field is the same as in vacuum, are slightly smaller than the well-known gas-phase dipole moments of HCN and HCCCN. A simple elliptical cavity model quantitatively accounts for this difference, which arises from the dipole-induced polarization of the helium.
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Affiliation(s)
- Paul L Stiles
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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47
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Dong F, Miller RE. Vibrational transition moment angles in isolated biomolecules: a structural tool. Science 2002; 298:1227-30. [PMID: 12424376 DOI: 10.1126/science.1076947] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Infrared spectroscopy is used extensively in the study of isolated biomolecules, but it becomes less useful as it is applied to systems of increasing complexity. Even if the individual vibrational bands can be resolved spectroscopically, their assignment becomes problematic when they are more closely spaced than can be determined using ab initio methods. We describe a method that helps to alleviate this difficulty by measuring the direction of the vibrational transition moment for each vibrational band. The molecules of interest (adenine and cytosine) are cooled to 0.37 kelvin in liquid helium nanodroplets and oriented in a large dc electric field. A polarized infrared laser is then used to determine the directions of the infrared transition moments relative to the permanent dipole moment. Comparisons with ab initio calculations provide detailed structural information, including experimental evidence for nonplanarity of adenine and three tautomers of cytosine.
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Affiliation(s)
- F Dong
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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48
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Tang J, Xu Y, McKellar ARW, Jäger W. Quantum solvation of carbonyl sulfide with helium atoms. Science 2002; 297:2030-3. [PMID: 12242436 DOI: 10.1126/science.1073718] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
High-resolution infrared and microwave spectra of He(N)-carbonyl sulfide (He(N)-OCS) clusters with N ranging from 2 to 8 have been detected and unambiguously assigned. The spectra show the formation of a solvation layer beginning with an equatorial "donut" of five helium atoms around the OCS molecule. The cluster moment of inertia increases as a function of N and overshoots the liquid droplet limit for N > 5, implying that even atoms in the first solvation shell are decoupled from the OCS rotation in helium nanodroplets. To the extent that this is due to superfluidity, the results directly explore the microscopic evolution of a phenomenon that is formally macroscopic in nature.
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Affiliation(s)
- Jian Tang
- Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
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49
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Callegari C, Lehmann KK, Schmied R, Scoles G. Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results. J Chem Phys 2001. [DOI: 10.1063/1.1418746] [Citation(s) in RCA: 320] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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