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Uenishi R, Horio T, Suzuki T. Time-Resolved Photoelectron Imaging of Acetone with 9.3 eV Photoexcitation. J Phys Chem A 2019; 123:6848-6853. [PMID: 31314525 DOI: 10.1021/acs.jpca.9b05179] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ultrafast electronic relaxation following 9.3 eV photoexcitation of gaseous acetone was investigated with time-resolved photoelectron imaging spectroscopy. An intense photoionization signal due to a transition from the 41A1(π,π*) state to the D1(π-1) cationic state diminishes within 50 fs, owing to vibrational wave packet motion leaving our observation energy window. Additional photoionization signals were assigned to transitions from Rydberg states with principal quantum numbers of 3-8 to the D0(n-1) cationic state, created by strong vibronic couplings with the bright 41A1(π,π*) state. The deactivation processes of the 41A1(π,π*) and Rydberg states are discussed based on their decay profiles obtained from a time-energy map of photoelectron kinetic energy distributions.
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Affiliation(s)
- Ryuta Uenishi
- Department of Chemistry, Graduate School of Science , Kyoto University , Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502 , Japan
| | - Takuya Horio
- Department of Chemistry, Graduate School of Science , Kyoto University , Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502 , Japan
| | - Toshinori Suzuki
- Department of Chemistry, Graduate School of Science , Kyoto University , Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502 , Japan
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2
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Hüter O, Temps F. Ultrafast α -CC bond cleavage of acetone upon excitation to 3p and 3d Rydberg states by femtosecond time-resolved photoelectron imaging. J Chem Phys 2018; 145:214312. [PMID: 28799347 DOI: 10.1063/1.4971243] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The radiationless electronic relaxation and α -CC bond fission dynamics of jet-cooled acetone in the S1 (nπ*) state and in high-lying 3p and 3d Rydberg states have been investigated by femtosecond time-resolved mass spectrometry and photoelectron imaging. The S1 state was accessed by absorption of a UV pump photon at selected wavelengths between λ = 320 and 250 nm. The observed acetone mass signals and the S1 photoelectron band decayed on sub-picosecond time scales, consistent with a recently proposed ultrafast structural relaxation of the molecules in the S1 state away from the Franck-Condon probe window. No direct signatures could be observed by the experiments for CC dissociation on the S1 potential energy hypersurface in up to 1 ns. The observed acetyl mass signals at all pump wavelengths turned out to be associated with absorption by the molecules of one or more additional pump and/or probe photons. In particular, absorption of a second UV pump photon by the S1 (nπ*) state was found to populate a series of high-lying states belonging to the n = 3 Rydberg manifold. The respective transitions are favored by much larger cross sections compared to the S1 ← S0 transition. The characteristic energies revealed by the photoelectron images allowed for assignments to the 3p and 3dyz states. At two-photon excitation energies higher than 8.1 eV, an ultrafast reaction pathway for breaking the α -CC bond in 50-90 fs via the 3dyz Rydberg state and the elusive ππ* state was observed, explaining the formation of acetyl radicals after femtosecond laser excitation of acetone at these wavelengths.
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Affiliation(s)
- O Hüter
- Institute of Physical Chemistry, Christian-Albrechts-University Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
| | - F Temps
- Institute of Physical Chemistry, Christian-Albrechts-University Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
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3
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Toulson BW, Fishman DA, Murray C. Photodissociation dynamics of acetone studied by time-resolved ion imaging and photofragment excitation spectroscopy. Phys Chem Chem Phys 2018; 20:2457-2469. [PMID: 29313039 DOI: 10.1039/c7cp07320h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photodissociation dynamics of acetone has been investigated using velocity-map ion imaging and photofragment excitation (PHOFEX) spectroscopy across a range of wavelengths spanning the first absorption band (236-308 nm). The radical products of the Norrish Type I dissociation, methyl and acetyl, as well as the molecular product ketene have been detected by single-photon VUV ionization at 118 nm. Ketene appears to be formed with non-negligible yield at all wavelengths, with a maximum value of Φ ≈ 0.3 at 280 nm. The modest translational energy release is inconsistent with dissociation over high barriers on the S0 surface, and ketene formation is tentatively assigned to a roaming pathway involving frustrated dissociation to the radical products. Fast-moving radical products are detected at λ ≤ 305 nm with total translational energy distributions that extend to the energetic limit, consistent with dissociation occurring near-exclusively on the T1 surface following intersystem crossing. At energies below the T1 barrier a statistical component indicative of S0 dissociation is observed, although dissociation via the S1/S0 conical intersection is absent at shorter wavelengths, in contrast to acetaldehyde. The methyl radical yield is enhanced over that of acetyl in PHOFEX spectra at λ ≤ 260 nm due to the onset of secondary dissociation of internally excited acetyl radicals. Time-resolved ion imaging experiments using picosecond duration pulses at 266 nm find an appearance time constant of τ = 1490 ± 140 ps for CH3 radicals formed on T1. The associated rate is representative of S1 → T1 intersystem crossing. At 284 nm, CH3 is formed on T1 with two distinct timescales: a fast <10 ns component is accompanied by a slower component with τ = 42 ± 7 ns. A two-step mechanism involving fast internal conversion, followed by slower intersystem crossing (S1 → S0 → T1) is proposed to explain the slow component.
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Affiliation(s)
- Benjamin W Toulson
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA.
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4
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Koch M, Thaler B, Heim P, Ernst WE. The Role of Rydberg-Valence Coupling in the Ultrafast Relaxation Dynamics of Acetone. J Phys Chem A 2017; 121:6398-6404. [PMID: 28737942 PMCID: PMC5608382 DOI: 10.1021/acs.jpca.7b05012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
![]()
The electronic structure
of excited states of acetone is represented
by a Rydberg manifold that is coupled to valence states which provide
very fast and efficient relaxation pathways. We observe and characterize
the transfer of population from photoexcited Rydberg states (6p, 6d,
7s) to a whole series of lower Rydberg states (3p to 4d) and a simultaneous
decay of population from these states. We obtain these results with
time-resolved photoelectron–photoion coincidence (PEPICO) detection
in combination with the application of Bayesian statistics for data
analysis. Despite the expectedly complex relaxation behavior, we find
that a simple sequential decay model is able to describe the observed
PEPICO transients satisfactorily. We obtain a slower decay (∼320
fs) from photoexcited states compared to a faster decay (∼100
fs) of states that are populated by internal conversion, demonstrating
that different relaxation dynamics are active. Within the series of
Rydberg states populated by internal conversion, the decay dynamics
seem to be similar, and a trend of slower decay from lower states
indicates an increasingly higher energy barrier along the decay pathway
for lower states. The presented results agree all in all with previous
relaxation studies within the Rydberg manifold. The state-resolved
observation of transient population ranging from 3p to 4d can serve
as reference for time-dependent simulations.
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Affiliation(s)
- Markus Koch
- Institute of Experimental Physics, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria
| | - Bernhard Thaler
- Institute of Experimental Physics, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria
| | - Pascal Heim
- 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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5
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Lee KLK, Nauta K, Kable SH. Photodissociation of acetone from 266 to 312 nm: Dynamics of CH3 + CH3CO channels on the S0 and T1 states. J Chem Phys 2017; 146:044304. [DOI: 10.1063/1.4974035] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Kin Long Kelvin Lee
- School of Chemistry, University of New South Wales, Kensington, New South Wales 2052, Australia
| | - Klaas Nauta
- School of Chemistry, University of New South Wales, Kensington, New South Wales 2052, Australia
| | - Scott H. Kable
- School of Chemistry, University of New South Wales, Kensington, New South Wales 2052, Australia
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6
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Maierhofer P, Bainschab M, Thaler B, Heim P, Ernst WE, Koch M. Disentangling Multichannel Photodissociation Dynamics in Acetone by Time-Resolved Photoelectron-Photoion Coincidence Spectroscopy. J Phys Chem A 2016; 120:6418-23. [PMID: 27459051 DOI: 10.1021/acs.jpca.6b07238] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
For the investigation of photoinduced dynamics in molecules with time-resolved pump-probe photoionization spectroscopy, it is essential to obtain unequivocal information about the fragmentation behavior induced by the laser pulses. We present time-resolved photoelectron-photoion coincidence (PEPICO) experiments to investigate the excited-state dynamics of isolated acetone molecules triggered by two-photon (269 nm) excitation. In the complex situation of different relaxation pathways, we unambiguously identify three distinct pump-probe ionization channels. The high selectivity of PEPICO detection allows us to observe the fragmentation behavior and to follow the time evolution of each channel separately. For channels leading to fragment ions, we quantitatively obtain the fragment-to-parent branching ratio and are able to determine experimentally whether dissociation occurs in the neutral molecule or in the parent ion. These results highlight the importance of coincidence detection for the interpretation of time-resolved photochemical relaxation and dissociation studies if multiple pathways are present.
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Affiliation(s)
- Paul Maierhofer
- Institute of Experimental Physics, Graz University of Technology, NAWI Graz , Petersgasse 16, 8010 Graz, Austria
| | - Markus Bainschab
- Institute of Experimental Physics, Graz University of Technology, NAWI Graz , Petersgasse 16, 8010 Graz, Austria
| | - Bernhard Thaler
- Institute of Experimental Physics, Graz University of Technology, NAWI Graz , Petersgasse 16, 8010 Graz, Austria
| | - Pascal Heim
- Institute of Experimental Physics, Graz University of Technology, NAWI Graz , Petersgasse 16, 8010 Graz, Austria
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, NAWI Graz , Petersgasse 16, 8010 Graz, Austria
| | - Markus Koch
- Institute of Experimental Physics, Graz University of Technology, NAWI Graz , Petersgasse 16, 8010 Graz, Austria
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7
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Fang Q, Shen L, Fang WH. Synchronous concerted multiple-body photodissociation of oxalyl chloride explored by ab initio-based dynamics simulations. J Chem Phys 2014; 139:024310. [PMID: 23862946 DOI: 10.1063/1.4812783] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Photo-induced multiple body dissociation is of fundamental interest in chemistry and physics. A description of the mechanism associated with n-body (n ≥ 3) photodissociation has proven to be an intriguing and yet challenging issue in the field of chemical dynamics. Oxalyl chloride, (ClCO)2, is the sole molecule reported up to date that can undergo four-body dissociation following absorption of a single UV photon, with a rich history of mechanistic debate. In the present work, the combined electronic structure calculations and dynamics simulations have been performed at the advanced level, which provides convincing evidence for resolving the mechanistic debate. More importantly, synchronous and asynchronous concertedness were explored for the first time for the (ClCO)2 photodissociation, which is based on the simulated time constants for the C-C and C-Cl bond fissions. Upon photoexcitation of (ClCO)2 to the S1 state, the adiabatic C-C or C-Cl fission takes place with little possibility. The four-body dissociation to 2Cl((2)P) and 2CO((1)Σ) was determined to a dominant channel with its branch of ∼0.7, while the three-body dissociation to ClCO((2)A(')) + CO((1)Σ) + Cl((2)P) was predicted to play a minor role in the (ClCO)2 photodissociation at 193 nm. Both the four-body and three-body dissociations are non-adiabatic processes, which proceed in a synchronous concerted way as a result of the S1 → S0 internal conversion. There is a little possibility for two-body dissociation to occur in the S0 and S1 states.
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Affiliation(s)
- Qiu Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
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8
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Exploring Multiple Potential Energy Surfaces: Photochemistry of Small Carbonyl Compounds. ACTA ACUST UNITED AC 2012. [DOI: 10.1155/2012/268124] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In theoretical studies of chemical reactions involving multiple potential energy surfaces (PESs) such as photochemical reactions, seams of intersection among the PESs often complicate the analysis. In this paper, we review our recipe for exploring multiple PESs by using an automated reaction path search method which has previously been applied to single PESs. Although any such methods for single PESs can be employed in the recipe, the global reaction route mapping (GRRM) method was employed in this study. By combining GRRM with the proposed recipe, all critical regions, that is, transition states, conical intersections, intersection seams, and local minima, associated with multiple PESs, can be explored automatically. As illustrative examples, applications to photochemistry of formaldehyde and acetone are described. In these examples as well as in recent applications to other systems, the present approach led to discovery of many unexpected nonadiabatic pathways, by which some complicated experimental data have been explained very clearly.
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Chin CH, Lee SH. Comparison of two-body and three-body decomposition of ethanedial, propanal, propenal, n-butane, 1-butene, and 1,3-butadiene. J Chem Phys 2012; 136:024308. [DOI: 10.1063/1.3675682] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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10
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Nádasdi R, Zügner GL, Farkas M, Dóbé S, Maeda S, Morokuma K. Photochemistry of Methyl Ethyl Ketone: Quantum Yields and S
1
/S
0
‐Diradical Mechanism of Photodissociation. Chemphyschem 2010; 11:3883-95. [DOI: 10.1002/cphc.201000522] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Rebeka Nádasdi
- Institute of Materials and Environmental Chemistry, Chemical Research Center of the Hungarian Academy of Sciences, Pusztaszeri út 59‐67, 1025 Budapest (Hungary), Fax: +36‐1‐438‐1147
| | - Gábor L. Zügner
- Institute of Materials and Environmental Chemistry, Chemical Research Center of the Hungarian Academy of Sciences, Pusztaszeri út 59‐67, 1025 Budapest (Hungary), Fax: +36‐1‐438‐1147
| | - Mária Farkas
- Institute of Materials and Environmental Chemistry, Chemical Research Center of the Hungarian Academy of Sciences, Pusztaszeri út 59‐67, 1025 Budapest (Hungary), Fax: +36‐1‐438‐1147
| | - Sándor Dóbé
- Institute of Materials and Environmental Chemistry, Chemical Research Center of the Hungarian Academy of Sciences, Pusztaszeri út 59‐67, 1025 Budapest (Hungary), Fax: +36‐1‐438‐1147
| | - Satoshi Maeda
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606‐8501 (Japan), Fax: +81‐75‐781‐4757
- The Hakubi Center, Kyoto University, Kyoto 606‐8501 (Japan)
| | - Keiji Morokuma
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606‐8501 (Japan), Fax: +81‐75‐781‐4757
- Department of Chemistry and Cherry L. Emerson Centre for Scientific Computation, Emory University, Atlanta, GA 30322 (USA)
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11
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Fang Q, Zhang F, Shen L, Fang WH, Luo Y. Photodissociation of phosgene: Theoretical evidence for the ultrafast and synchronous concerted three-body process. J Chem Phys 2009; 131:164306. [DOI: 10.1063/1.3253048] [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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12
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Ho JW, Chen WK, Cheng PY. Unraveling Complex Three-Body Photodissociation Dynamics of Dimethyl Sulfoxide: A Femtosecond Time-Resolved Spectroscopic Study. J Phys Chem A 2008; 112:10453-68. [DOI: 10.1021/jp804847y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jr-Wei Ho
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, R. O. C
| | - Wei-Kan Chen
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, R. O. C
| | - Po-Yuan Cheng
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, R. O. C
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13
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Goncharov V, Herath N, Suits AG. Roaming Dynamics in Acetone Dissociation. J Phys Chem A 2008; 112:9423-8. [DOI: 10.1021/jp802534r] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Vasiliy Goncharov
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202
| | - Nuradhika Herath
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202
| | - Arthur G. Suits
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202
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14
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Park ST, Feenstra JS, Zewail AH. Ultrafast electron diffraction: Excited state structures and chemistries of aromatic carbonyls. J Chem Phys 2006; 124:174707. [PMID: 16689590 DOI: 10.1063/1.2194017] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The photophysics and photochemistry of molecules with complex electronic structures, such as aromatic carbonyls, involve dark structures of radiationless processes. With ultrafast electron diffraction (UED) of isolated molecular beams it is possible to determine these transient structures, and in this contribution we examine the nature of structural dynamics in two systems, benzaldehyde and acetophenone. Both molecules are seen to undergo a bifurcation upon excitation (S(2)). Following femtosecond conversion to S(1), the bifurcation leads to the formation of molecular dissociation products, benzene and carbon monoxide for benzaldehyde, and benzoyl and methyl radicals for acetophenone, as well as intersystem crossing to the triplet state in both cases. The structure of the triplet state was determined to be "quinoidlike" of pipi(*) character with the excitation being localized in the phenyl ring. For the chemical channels, the product structures were also determined. The difference in photochemistry between the two species is discussed with respect to the change in large amplitude motion caused by the added methyl group in acetophenone. This discussion is also expanded to compare these results with the prototypical aliphatic carbonyl compounds, acetaldehyde and acetone. From these studies of structural dynamics, experimental and theoretical, we provide a landscape picture for, and the structures involved in, the radiationless pathways which determine the fate of molecules following excitation. For completeness, the UED methodology and the theoretical framework for structure determination are described in this full account of an earlier communication [J. S. Feenstra et al., J. Chem. Phys. 123, 221104 (2005)].
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Affiliation(s)
- Sang Tae Park
- Laboratory for Molecular Science, and Physical Biology Center for Ultrafast Science and Technology, California Institute of Technology, Pasadena, California 91125, USA
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15
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Chen WK, Ho JW, Cheng PY. Isotope effects in the ultrafast photodissociation of acetone 3s Rydberg state excited at 195nm. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.09.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Chen WK, Ho JW, Cheng PY. Ultrafast Photodissociation Dynamics of Acetone at 195 nm: I. Initial-state, Intermediate, and Product Temporal Evolutions by Femtosecond Mass-Selected Multiphoton Ionization Spectroscopy. J Phys Chem A 2005; 109:6805-17. [PMID: 16834036 DOI: 10.1021/jp050969f] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The photodissociation dynamics of the acetone S2 (n, 3s) Rydberg state excited at 195 nm has been studied by using femtosecond pump-probe mass-selected multiphoton ionization spectroscopy. For the first time, the temporal evolutions of the initial state, intermediates, and methyl products were simultaneously measured and analyzed for this reaction to elucidate the complex dynamics. Two mechanisms were considered: (1) the commonly accepted mechanism in which the primary dissociation occurs on the first triplet-state surface, and (2) the recently proposed mechanism in which the primary dissociation takes place on the first singlet-excited-state surface. Our results and analyses supported the validity of the new mechanism. On the other hand, the conventional mechanism was found to be inadequate to describe the observed dynamics. The temporal evolution of methyl products arising from the secondary dissociation of hot acetyl intermediates exhibited a very complex behavior that can be ascribed to the combination of a nonuniform initial vibrational distribution and the competition between dissociation and slow intramolecular vibrational redistribution.
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Affiliation(s)
- Wei-Kan Chen
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, ROC
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