Abstract
Raman studies of diphenylhexatriene in the first excited singlet state evidence strong vibronic coupling between two close 1Bu/2Ag states. The geometrical change after photoexcitation contains a dominant contribution of a low-frequency mode with bu symmetry near 40 cm-1. This mode is identified as a relatively strong line in the Raman spectrum. Vibronic coupling mainly affects two C=C stretching Raman bands near 1700 cm-1. A two-dimensional effective potential for the lowest excited singlet state is derived which models the coupling between the coordinate of the 40 cm-1 mode and the C=C stretching coordinate, thereby explaining the occurrence of the two bands and their strong solvent shift. The model gives, in the zero gap limit, a double-well potential for the C=C stretching coordinate, due to the pseudo-Jahn-Teller effect. Modulation of this potential by the low-frequency cycle explains the spectral broadening observed in the Raman spectra.
Original language | English (US) |
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Pages (from-to) | 56-62 |
Number of pages | 7 |
Journal | Chemical Physics Letters |
Volume | 295 |
Issue number | 1-2 |
State | Published - Oct 2 1998 |
Externally published | Yes |
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Spectroscopy
- Atomic and Molecular Physics, and Optics