Following the excited state relaxation dynamics of indole and 5-hydroxyindole using time-resolved photoelectron spectroscopy

Ruth Livingstone, Oliver Schalk, Andrey E. Boguslavskiy, Guorong Wu, Lisa Therese Bergendahl, Albert Stolow, Martin J. Paterson, David Townsend

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Abstract

Time-resolved photoelectron spectroscopy was used to obtain new information about the dynamics of electronic relaxation in gas-phase indole and 5-hydroxyindole following UV excitation with femtosecond laser pulses centred at 249 nm and 273 nm. Our analysis of the data was supported by ab initio calculations at the coupled cluster and complete-active-space self-consistent-field levels. The optically bright 1L(a) and 1L(b) electronic states of 1 pi pi* character and spectroscopically dark and dissociative 1 pi sigma* states were all found to play a role in the overall relaxation process. In both molecules we conclude that the initially excited 1L(a) state decays non-adiabatically on a sub 100 fs timescale via two competing pathways, populating either the subsequently long-lived 1L(b) state or the 1 pi sigma* state localised along the N-H coordinate, which exhibits a lifetime on the order of 1 ps. In the case of 5-hydroxyindole, we conclude that the 1 pi sigma* state localised along the O-H coordinate plays little or no role in the relaxation dynamics at the two excitation wavelengths studied. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3659231]

Original languageEnglish
Article number194307
Pages (from-to)-
Number of pages12
JournalJournal of Chemical Physics
Volume135
Issue number19
DOIs
Publication statusPublished - 21 Nov 2011

Keywords

  • ab initio calculations
  • coupled cluster calculations
  • dark states
  • excited states
  • molecule-photon collisions
  • multiphoton processes
  • organic compounds
  • photoexcitation
  • SCF calculations
  • time resolved spectra
  • ultraviolet photoelectron spectra
  • VAN-DER-WAALS
  • PHOTOFRAGMENT TRANSLATIONAL SPECTROSCOPY
  • FLUORESCENCE EXCITATION-SPECTRA
  • H-ATOM ELIMINATION
  • ELECTRONIC-SPECTRA
  • ABSORPTION-SPECTRA
  • SUBSTITUTED INDOLES
  • GAS-PHASE
  • AB-INITIO
  • JET

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