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Mandal S, Gopal R, Srinivas H, D'Elia A, Sen A, Sen S, Richter R, Coreno M, Bapat B, Mudrich M, Sharma V, Krishnan SR. Coincident angle-resolved state-selective photoelectron spectroscopy of acetylene molecules: a candidate system for time-resolved dynamics. Faraday Discuss 2021; 228:242-265. [PMID: 33687396 DOI: 10.1039/d0fd00120a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The acetylene-vinylidene system serves as a benchmark for investigations of ultrafast dynamical processes where the coupling of the electronic and nuclear degrees of freedom provides a fertile playground to explore the femto- and sub-femto-second physics with coherent extreme-ultraviolet (EUV) photon sources both on the table-top as well as free-electron lasers. We focus on detailed investigations of this molecular system in the photon energy range 19-40 eV where EUV pulses can probe the dynamics effectively. We employ photoelectron-photoion coincidence (PEPICO) spectroscopy to uncover hitherto unrevealed aspects of this system. In this work, the role of excited states of the C2H2+ cation, the primary photoion, is specifically addressed. From photoelectron energy spectra and angular distributions, the nature of the dissociation and isomerization channels is discerned. Exploiting the 4π-collection geometry of the velocity map imaging spectrometer, we not only probe pathways where the efficiency of photoionization is inherently high but also perform PEPICO spectroscopy on relatively weak channels.
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Affiliation(s)
- S Mandal
- Indian Institute of Science Education and Research, Pune 411008, India
| | - R Gopal
- Tata Institute of Fundamental Research, Hyderabad 500107, India
| | - H Srinivas
- Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany
| | - A D'Elia
- IOM-CNR, Laboratorio TASC, Basovizza SS-14, km 163.5, 34149 Trieste, Italy
| | - A Sen
- Indian Institute of Science Education and Research, Pune 411008, India
| | - S Sen
- Indian Institute of Technology Hyderabad, Kandi 502285, India.
| | - R Richter
- Elettra-Sincrotrone Trieste, 34149 Basovizza, Italy
| | - M Coreno
- Istituto di Struttura della Materia - Consiglio Nazionale delle Ricerche (ISM-CNR), 34149 Trieste, Italy and INFN-LNF, via Enrico Fermi 54, 00044 Frascati, Italy
| | - B Bapat
- Indian Institute of Science Education and Research, Pune 411008, India
| | - M Mudrich
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark and Department of Physics, QuCenDiEm-Group, Indian Institute of Technology Madras, Chennai 600036, India.
| | - V Sharma
- Indian Institute of Technology Hyderabad, Kandi 502285, India.
| | - S R Krishnan
- Department of Physics, QuCenDiEm-Group, Indian Institute of Technology Madras, Chennai 600036, India.
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Jiang YH, Rudenko A, Herrwerth O, Foucar L, Kurka M, Kühnel KU, Lezius M, Kling MF, van Tilborg J, Belkacem A, Ueda K, Düsterer S, Treusch R, Schröter CD, Moshammer R, Ullrich J. Ultrafast extreme ultraviolet induced isomerization of acetylene cations. PHYSICAL REVIEW LETTERS 2010; 105:263002. [PMID: 21231652 DOI: 10.1103/physrevlett.105.263002] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Indexed: 05/21/2023]
Abstract
Ultrafast isomerization of acetylene cations ([HC=CH](+)) in the low-lying excited A(2)Σ(g)(+) state, populated by the absorption of extreme ultraviolet (XUV) photons (38 eV), has been observed at the Free Electron Laser in Hamburg, (FLASH). Recording coincident fragments C(+) + CH2(+) as a function of time between XUV-pump and -probe pulses, generated by a split-mirror device, we find an isomerization time of 52±15 fs in a kinetic energy release (KER) window of 5.8<KER<8 eV, providing clear evidence for the existence of a fast, nonradiative decay channel.
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Affiliation(s)
- Y H Jiang
- Max-Planck-Institut für Kernphysik, Heidelberg, Germany
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Gridelet E, Lorquet AJ, Locht R, Lorquet JC, Leyh B. Hydrogen Atom Loss from the Benzene Cation. Why Is the Kinetic Energy Release so Large? J Phys Chem A 2006; 110:8519-27. [PMID: 16821836 DOI: 10.1021/jp056119h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The kinetic energy release distributions (KERDs) associated with the hydrogen loss from the benzene cation and the deuterium loss from the perdeuteriobenzene cation have been remeasured on the metastable time scale and analyzed by the maximum entropy method. The experimental kinetic energy releases are larger than expected statistically, in contradistinction to what has been observed for the C-X fragmentations of the halogenobenzene cations. H(D) loss from C(6)H(6)(+) (C(6)D(6)(+)) occurs via a conical intersection connecting the (2)A(2) and (2)A(1) electronic states. Two models are proposed to account for the experimental data: (i) a modified orbiting transition state theory (OTST) approach incorporating electronic nonadiabaticity; (ii) an electronically nonadiabatic version of the statistical adiabatic channel model (SACM) of Quack and Troe. The latter approach is found to be preferable. It leads to the conclusion that the larger the energy stored in the transitional modes, which partly convert to the relative interfragment motion, the shorter the value of the reaction coordinate at which the adiabatic channels cross, and the larger the probability of undergoing the (2)A(2) --> (2)A(1) transition required for hydrogen loss.
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Affiliation(s)
- E Gridelet
- Department of Chemistry, Molecular Dynamics Laboratory, University of Liège, B-4000 Sart-Tilman, Belgium
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Gridelet E, Dehareng D, Locht R, Lorquet AJ, Lorquet JC, Leyh B. Ground and Excited State Dissociation Dynamics of Ionized 1,1-Difluoroethene. J Phys Chem A 2005; 109:8225-35. [PMID: 16834209 DOI: 10.1021/jp051542b] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The kinetic energy release distributions (KERDs) for the fluorine atom loss from the 1,1-difluoroethene cation have been recorded with two spectrometers in two different energy ranges. A first experiment uses dissociative photoionization with the He(I) and Ne(I) resonance lines, providing the ions with a broad internal energy range, up to 7 eV above the dissociation threshold. The second experiment samples the metastable range, and the average ion internal energy is limited to about 0.2 eV above the threshold. In both energy domains, KERDs are found to be bimodal. Each component has been analyzed by the maximum entropy method. The narrow, low kinetic energy components display for both experiments the characteristics of a statistical, simple bond cleavage reaction: constraint equal to the square root of the fragment kinetic energy and ergodicity index higher than 90%. Furthermore, this component is satisfactorily accounted for in the metastable time scale by the orbiting transition state theory. Potential energy surfaces corresponding to the five lowest electronic states of the dissociating 1,1-C2H2F2+ ion have been investigated by ab initio calculations at various levels. The equilibrium geometry of these states, their dissociation energies, and their vibrational wavenumbers have been calculated, and a few conical intersections between these surfaces have been identified. It comes out that the ionic ground state X2B1 is adiabatically correlated with the lowest dissociation asymptote. Its potential energy curve increases in a monotonic way along the reaction coordinate, giving rise to the narrow KERD component. Two states embedded in the third photoelectron band (B2A1 at 15.95 eV and C2B2 at 16.17 eV) also correlate with the lowest asymptote at 14.24 eV. We suggest that their repulsive behavior along the reaction coordinate be responsible for the KERD high kinetic energy contribution.
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Affiliation(s)
- E Gridelet
- Department of Chemistry, Molecular Dynamics Laboratory, Building B6c, and Centre for Protein Engineering, Building B6a, University of Liège, B-4000 SART-TILMAN, Belgium
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Chiu YH, Dressler RA, Levandier DJ, Williams S, Murad E. Collision energy dependence and product recoil velocity analysis of O+(4S)+C2H2 charge-transfer and chemical reaction channels. J Chem Phys 1998. [DOI: 10.1063/1.477148] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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