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Manifestation of conical intersections in resonance Raman intensities
Author(s) -
Chowdary Praveen D.,
Umapathy Siva
Publication year - 2010
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2442
Subject(s) - conical intersection , polyatomic ion , resonance (particle physics) , conical surface , excited state , excitation , raman spectroscopy , molecular vibration , atomic physics , femtosecond , pyrazine , raman scattering , chemistry , symmetry (geometry) , molecular physics , physics , ion , laser , optics , quantum mechanics , materials science , geometry , mathematics , stereochemistry , composite material
This paper deals with the manifestations of conical intersections (CIs), unequivocal spectroscopic signatures of which are still elusive, in the resonance Raman intensities. In particular, the results of our calculations on the ‘two state‐two vibrational mode’ and the ‘two state‐three vibrational mode’ models are presented. The models comprise two excited states of different spatial symmetry, one bright and one dark, which are coupled by a nontotally symmetric mode while the energy gap between them is tuned by one/two totally symmetric modes. Time dependent theory for vibronically coupled states is employed for the calculation and analysis of Raman excitation profiles (REPs). The manifestation of intersections in REPs is studied by extensive model calculations and the results of two specific models are presented. The feasibility of using REPs to probe the role of CIs in polyatomic systems is ascertained by multimode calculations on two polyatomic systems viz., pyrazine and trans ‐azobenzene. The study also notes the importance of the pump excitation wavelength dependence in a femtosecond time‐resolved experiment probing the intersection‐induced nonadiabatic dynamics. Copyright © 2009 John Wiley & Sons, Ltd.