Excited-State Dynamics of 8 '-Apo-beta-caroten-8 '-al and 7 ',7 '-Dicyano-7 '-apo-beta-carotene Studied by Femtosecond Time-Resolved Infrared Spectroscopy

Pang, Yoonsoo, Prantil, Matthew A., Van Tassle, Aaron J., Jones, Garth A. and Fleming, Graham R. (2009) Excited-State Dynamics of 8 '-Apo-beta-caroten-8 '-al and 7 ',7 '-Dicyano-7 '-apo-beta-carotene Studied by Femtosecond Time-Resolved Infrared Spectroscopy. The Journal of Physical Chemistry B, 113 (39). pp. 13086-13095. ISSN 1520-6106

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We present infrared transient absorption measurements of the substituted apocarotenoids 8'-apo-beta-caroten-8'-al (I) and 7',7'-dicyano-7'-apo-beta-carotene (II) in the S-1 excited states by one-photon excitation (1PE) and two-photon excitation (2PE). 1PE populates the higher S-2 state, which converts to the S-1 state via rapid internal conversion, and 2PE populates the S-1 state directly. The 1PE-prepared population returns to the ground state on a similar to 19 ps time scale in I and a similar to 2.0 ps time scale in II. Distinct vibrational spectra and dynamics are observed from the 2PE-prepared S-1 state for both I and II: the symmetric C=C stretching vibration around 1500 cm(-1) in the S-1 state is several-fold increased in strength over other C=C stretching modes compared to the 1PE case, and long-lived absorptions are observed even after all the excited-state populations have decayed. The lifetimes of the S-1 state prepared by 2PE are slightly shorter (similar to 17 ps for I and similar to 1.7 ps for II) than the 1PE values. It is proposed that I PE and 2PE lead to the Population of different conformational minima of the S-1 potential surface. These two minima do not communicate on the time scale of the S-1 lifetime and have different relaxation channels on the ground-state surface.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Depositing User: Rachel Smith
Date Deposited: 20 Apr 2011 15:01
Last Modified: 09 Feb 2023 13:35
URI: https://ueaeprints.uea.ac.uk/id/eprint/29770
DOI: 10.1021/jp905758e

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