Strong vibronic coupling in the first excited singlet state of diphenylhexatriene by an asymmetric low-frequency mode

M. Pfeiffer, W. Werncke, Sebastian Wachsmann-Hogiu, A. Kummrow, A. Lau

Research output: Contribution to journalArticle

13 Scopus citations

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 languageEnglish (US)
Pages (from-to)56-62
Number of pages7
JournalChemical Physics Letters
Volume295
Issue number1-2
StatePublished - Oct 2 1998
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Spectroscopy
  • Atomic and Molecular Physics, and Optics

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