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Theoretical Calculations on Vibrational Frequencies and Absorption Spectra of S 1 and S 2 States of Pyridine
Author(s) -
Wu DeYin,
Hayashi Michitoshi,
Shiu YingJen,
Liang KuoKan,
Chang ChungHung,
Lin ShengHsien
Publication year - 2003
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.200300105
Subject(s) - chemistry , excited state , ab initio , complete active space , potential energy , atomic physics , normal mode , ground state , singlet state , absorption spectroscopy , spectral line , molecular vibration , ab initio quantum chemistry methods , molecular physics , vibration , computational chemistry , basis set , density functional theory , quantum mechanics , physics , molecule , organic chemistry
Three harmonic potential‐energy surfaces of 1 A 1 , 1 B 1 , and 1 B 2 singlet states of pyridine have been obtained by using ab initio method. Geometric properties and force fields of these states have been determined with the complete‐active‐space self‐consistent‐field (CASSCF) theoretical method. Vibrational frequencies of two excited states have been assigned on the basis of the potential energy distribution from normal mode analysis. The resulting properties are used to simulate the experimental absorption spectrum. From the spectral simulation the totally symmetric vibrations with large Huang‐Rhys factors have been identified as ν 12 and ν 6a modes in the 1 B 1 state; ν 1 and ν 12 modes in the 1 B 2 state, indicating that these modes have strong vibronic coupling between ground and excited states.