The role of the nπ* 1Au state in the photoabsorption and relaxation of pyrazine
Journal
Chemistry - An Asian Journal
Journal Volume
6
Journal Issue
11
Pages
2977-2985
Date Issued
2011
Author(s)
Abstract
The geometric, energetic, and spectroscopic properties of the ground state and the lowest four singlet excited states of pyrazine have been studied by using DFT/TD-DFT, CASSCF, CASPT2, and related quantum chemical calculations. The second singlet n?* state, 1Au, which is conventionally regarded dark due to the dipole-forbidden 1A u??Ag transition, has been investigated in detail. Our new simulation has shown that the state could be visible in the absorption spectrum by intensity borrowing from neighboring n?* 1B3u and ??* 1B2u states through vibronic coupling. The scans on potential-energy surfaces further indicated that the 1Au state intersects with the 1B2u states near the equilibrium of the latter, thus implying its participation in the ultrafast relaxation process. ? 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Subjects
absorption; excited states; pyrazines; quantum chemistry; vibronic coupling
SDGs
Other Subjects
Absorption; Absorption spectroscopy; Excited states; Ground state; Potential energy; Quantum chemistry; Intensity borrowing; Photoabsorptions; Pyrazines; Quantum chemical calculations; Singlet excited state; Spectroscopic property; Ultrafast relaxation; Vibronic coupling; Quantum theory
Type
journal article