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Title: Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

Abstract

The dynamics of pyrrole excited at wavelengths in the range 242-217 nm are studied using a combination of time-resolved photoelectron spectroscopy and wavepacket propagations performed using the multi-configurational time-dependent Hartree method. Excitation close to the origin of pyrrole’s electronic spectrum, at 242 and 236 nm, is found to result in an ultrafast decay of the system from the ionization window on a single timescale of less than 20 fs. This behaviour is explained fully by assuming the system to be excited to the A{sub 2}(πσ{sup ∗}) state, in accord with previous experimental and theoretical studies. Excitation at shorter wavelengths has previously been assumed to result predominantly in population of the bright A{sub 1}(ππ{sup ∗}) and B{sub 2}(ππ{sup ∗}) states. We here present time-resolved photoelectron spectra at a pump wavelength of 217 nm alongside detailed quantum dynamics calculations that, together with a recent reinterpretation of pyrrole’s electronic spectrum [S. P. Neville and G. A. Worth, J. Chem. Phys. 140, 034317 (2014)], suggest that population of the B{sub 1}(πσ{sup ∗}) state (hitherto assumed to be optically dark) may occur directly when pyrrole is excited at energies in the near UV part of its electronic spectrum. The B{sub 1}(πσ{sup ∗}) state is foundmore » to decay on a timescale of less than 20 fs by both N-H dissociation and internal conversion to the A{sub 2}(πσ{sup ∗}) state.« less

Authors:
 [1];  [2];  [2]; ;  [3];  [1];  [4];  [1];  [5];  [6];  [1];  [7]
  1. National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada)
  2. (China)
  3. School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)
  4. (Sweden)
  5. (Japan)
  6. School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom)
  7. (Canada)
Publication Date:
OSTI Identifier:
22416144
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 7; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DISSOCIATION; EXCITATION; EXCITED STATES; HARTREE-FOCK METHOD; INTERNAL CONVERSION; PHOTOELECTRON SPECTROSCOPY; PYRROLES; TIME DEPENDENCE; TIME RESOLUTION; WAVE PACKETS

Citation Formats

Wu, Guorong, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, Neville, Simon P., Worth, Graham A., E-mail: g.a.worth@bham.ac.uk, Schalk, Oliver, Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 109 61 Stockholm, Sekikawa, Taro, Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628, Ashfold, Michael N. R., Stolow, Albert, E-mail: astolow@uottawa.ca, and Departments of Chemistry and Physics, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5. Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study. United States: N. p., 2015. Web. doi:10.1063/1.4907529.
Wu, Guorong, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, Neville, Simon P., Worth, Graham A., E-mail: g.a.worth@bham.ac.uk, Schalk, Oliver, Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 109 61 Stockholm, Sekikawa, Taro, Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628, Ashfold, Michael N. R., Stolow, Albert, E-mail: astolow@uottawa.ca, & Departments of Chemistry and Physics, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5. Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study. United States. doi:10.1063/1.4907529.
Wu, Guorong, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, Neville, Simon P., Worth, Graham A., E-mail: g.a.worth@bham.ac.uk, Schalk, Oliver, Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 109 61 Stockholm, Sekikawa, Taro, Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628, Ashfold, Michael N. R., Stolow, Albert, E-mail: astolow@uottawa.ca, and Departments of Chemistry and Physics, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5. 2015. "Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study". United States. doi:10.1063/1.4907529.
@article{osti_22416144,
title = {Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study},
author = {Wu, Guorong and State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 and Neville, Simon P. and Worth, Graham A., E-mail: g.a.worth@bham.ac.uk and Schalk, Oliver and Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 109 61 Stockholm and Sekikawa, Taro and Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628 and Ashfold, Michael N. R. and Stolow, Albert, E-mail: astolow@uottawa.ca and Departments of Chemistry and Physics, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5},
abstractNote = {The dynamics of pyrrole excited at wavelengths in the range 242-217 nm are studied using a combination of time-resolved photoelectron spectroscopy and wavepacket propagations performed using the multi-configurational time-dependent Hartree method. Excitation close to the origin of pyrrole’s electronic spectrum, at 242 and 236 nm, is found to result in an ultrafast decay of the system from the ionization window on a single timescale of less than 20 fs. This behaviour is explained fully by assuming the system to be excited to the A{sub 2}(πσ{sup ∗}) state, in accord with previous experimental and theoretical studies. Excitation at shorter wavelengths has previously been assumed to result predominantly in population of the bright A{sub 1}(ππ{sup ∗}) and B{sub 2}(ππ{sup ∗}) states. We here present time-resolved photoelectron spectra at a pump wavelength of 217 nm alongside detailed quantum dynamics calculations that, together with a recent reinterpretation of pyrrole’s electronic spectrum [S. P. Neville and G. A. Worth, J. Chem. Phys. 140, 034317 (2014)], suggest that population of the B{sub 1}(πσ{sup ∗}) state (hitherto assumed to be optically dark) may occur directly when pyrrole is excited at energies in the near UV part of its electronic spectrum. The B{sub 1}(πσ{sup ∗}) state is found to decay on a timescale of less than 20 fs by both N-H dissociation and internal conversion to the A{sub 2}(πσ{sup ∗}) state.},
doi = {10.1063/1.4907529},
journal = {Journal of Chemical Physics},
number = 7,
volume = 142,
place = {United States},
year = 2015,
month = 2
}
  • The dynamics of N-methylpyrrole following excitation at wavelengths in the range 241.5-217.0 nm were studied using a combination of time-resolved photoelectron spectroscopy (TRPES), ab initio quantum dynamics calculations using the multi-layer multi-configurational time-dependent Hartree method, as well as high-level photoionization cross section calculations. Excitation at 241.5 and 236.2 nm results in population of the A{sub 2}(πσ{sup ∗}) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B{sub 1}(π3p{sub y}) Rydberg state, followed by prompt internal conversion to the A{sub 2}(πσ{sup ∗}) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacketmore » in the A{sub 2}(πσ{sup ∗}) state was found to vary with excitation wavelength, decreasing by one order of magnitude upon tuning from 241.5 nm to 236.2 nm and by more than three orders of magnitude when excited at 217.0 nm. The order of magnitude difference in lifetimes measured at the longer excitation wavelengths is attributed to vibrational excitation in the A{sub 2}(πσ{sup ∗}) state, facilitating wavepacket motion around the potential barrier in the N–CH{sub 3} dissociation coordinate.« less
  • The excited-state dynamics of furan were studied by time-resolved photoelectron imaging using a sub-20-fs deep UV (198 nm) and vacuum UV (159 nm) light source. The 198- and 159-nm pulses produce photoionization signals in both pump-probe and probe-pump pulse sequences. When the 198-nm pulse precedes the 159-nm pulse, it creates the {sup 1}A{sub 2}(3s) Rydberg and {sup 1}B{sub 2}(ππ{sup ∗}) valence states, and the former decays exponentially with a time constant of about 20 fs whereas the latter exhibits more complex wave-packet dynamics. When the 159-nm pulse precedes the 198-nm pulse, a wave packet is created on the {sup 1}A{submore » 1}(ππ{sup ∗}) valence state, which rapidly disappears from the observation window owing to structural deformation. The 159-nm photoexcitation also creates the 3s and 3p{sub x,y} Rydberg states non-adiabatically.« less
  • Time-resolved resonance Raman spectra of the lowest excited triplet state, T{sub 1}, the radical cation, R{sup {sm_bullet}+}, and the radical anion, R{sup {sm_bullet}{minus}}, of diphenylacetylene (DPA) have been measured. Vibrational assignments of the Raman bands of these transients have been based on the frequency shifts on phenyl deuterations and {sup 13}C substitution of the C{triple_bond}C triple bond. The Raman spectra have shown that the C{triple_bond}C stretch exhibits large low-frequency shifts in the order, S{sub 0} (2217 cm{sup {minus}1}), R{sup {sm_bullet}+} (2142 cm{sup {minus}1}), R{sup {sm_bullet}{minus}} (2091 cm{sup {minus}1}), and T{sub 1} (1972 cm{sup {minus}1}), indicating that the C{triple_bond}C triple bondmore » weakens dramatically in this sequence. The same trend, though not large, has been observed for phenyl skeletal vibrations as well. The dependence of the yield of R{sup {sm_bullet}+} on the pump laser power has revealed that the photoionization of DPA to produce R{sup {sm_bullet}+} is a biphotonic ionization can occur through the T{sub 1} state. 21 refs., 10 figs., 1 tab.« less