Investigation of electronically excited indole relaxation dynamics via photoionization and fragmentation pump-probe spectroscopy
- Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States)
The studies herein investigate the involvement of the low-lying {sup 1}L{sub a} and {sup 1}L{sub b} states with {sup 1}ππ{sup *} character and the {sup 1}πσ{sup *} state in the deactivation process of indole following photoexcitation at 201 nm. Three gas-phase, pump-probe spectroscopic techniques are employed: (1) Time-resolved photoelectron spectroscopy (TR-PES), (2) hydrogen atom (H-atom) time-resolved kinetic energy release (TR-KER), and (3) time-resolved ion yield (TR-IY). Each technique provides complementary information specific to the photophysical processes in the indole molecule. In conjunction, a thorough examination of the electronically excited states in the relaxation process, with particular focus on the involvement of the {sup 1}πσ{sup *} state, is afforded. Through an extensive analysis of the TR-PES data presented here, it is deduced that the initial excitation of the {sup 1}B{sub b} state decays to the {sup 1}L{sub a} state on a timescale beyond the resolution of the current experimental setup. Relaxation proceeds on the {sup 1}L{sub a} state with an ultrafast decay constant (<100 femtoseconds (fs)) to the lower-lying {sup 1}L{sub b} state, which is found to possess a relatively long lifetime of 23 ± 5 picoseconds (ps) before regressing to the ground state. These studies also manifest an additional component with a relaxation time of 405 ± 76 fs, which is correlated with activity along the {sup 1}πσ{sup *} state. TR-KER and TR-IY experiments, both specifically probing {sup 1}πσ{sup *} dynamics, exhibit similar decay constants, further validating these observations.
- OSTI ID:
- 22419942
- Journal Information:
- Journal of Chemical Physics, Vol. 141, Issue 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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