Analysis of the role of nonstationary vibrational states in condensed phase photochemistry: The rhodopsin paradigm
- Lawrence Berkeley National Lab., CA (United States); and others
Nonstationary vibrational states can play a significant role in reactive internal conversion processes in condensed phase photochemical and photobiological reactions. In this limit, the initial Franck-condon-driven nuclear dynamics, the nuclear dynamics in the transition region, the final photoisomerization dynamics, and quantum yield are mechanistically linked. Application to the visual pigment rhodopsin are appealing because of the wealth of available data and the importance of the system. A 28 mode model has been developed from the RR intensity data that includes recently assigned modes at 260 and 568 cm{sup -1} that are reactive C{sub 10}-C{sub 11} + C{sub 12}-C{sub 13} and C{sub 11}=C{sub 12} torsions, respectively. The evolution of the system after excitation is followed by calculations of dynamic absorption spectra and spontaneous emission spectra. To test the hypothesis that non-bonded steric interactions between the C{sub 10}H and the C{sub 13}H{sub 3} groups of the 11-cis retinal chromophore are responsible for driving the rapid isomerization dynamics, we recently examined 13-dimethyl pigments. Removal of the C{sub 13}H{sub 3} group leads to a decrease of the C{sub 11}=C{sub 12} torsional Raman intensities, an increase of the isomerization time from 200 fs to 400 fs, and a reduced isomerization quantum yield (0.47) consistent with a dynamic isomerization time from 200 fs to 400 fs, and a reduced isomerization quantum yield (0.47) consistent with a dynamic isomerization mechanism. The analysis method presented here should be valuable in understanding the role of vibrational coherence in other condensed phase reactions such as photosynthetic electron transfer.
- OSTI ID:
- 539075
- Report Number(s):
- CONF-960807-; TRN: 97:004029-0144
- Resource Relation:
- Conference: 212. national meeting of the American Chemical Society (ACS), Orlando, FL (United States), 25-30 Aug 1996; Other Information: PBD: 1996; Related Information: Is Part Of 212th ACS national meeting; PB: 1830 p.
- Country of Publication:
- United States
- Language:
- English
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