Vibronic coupling and Raman intensity of naphthalene and anthracene

Nobuhiro Ohta*, Mitsuo Ito

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

The intensities of Raman lines of naphthalene and anthracene have been measured with exciting light of various wavelengths in the pre-resonance region. Great Raman intensity enhancements are found for the b3g Raman line at 1629 cm-1 and two totally symmetric Raman lines at 1579 and 1381 cm-1 of naphthalene and for the corresponding Raman lines of anthracene. It is found that the Raman intensities of the b3g vibrations are mainly responsible for the vibronic coupling between two π,π* excited states 1B1u (1La) and 1B2u(1Bb) of these molecules. In the longer wavelength region, the b3g Raman line of naphthalene exhibits an "intensity de-enhancement" in contrast to the great intensity enhancement in the shorter wavelength region. The observed "de-enhancement" is explained as the result of destructive interference of two different vibronic coupling mechanisms. The intensity enhancements of the ag Raman lines are found to be reflecting the geometrical structures of the molecules in their 1B1u(1La) states.

Original languageEnglish
Pages (from-to)71-81
Number of pages11
JournalChemical Physics
Volume20
Issue number1
DOIs
StatePublished - 15 Feb 1977

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