The Raman excitation profile spectrum of β-carotene in the preresonance region: Evidence for a low-lying singlet state

Abstract

The Raman excitation profile spectrum of the ν₁ band of trans‐β‐carotene has been obtained in the preresonance region (16 900–19 000 cm⁻¹). Five features are found in the spectrum which are interpreted as vibrational structure of a low‐lying excited ¹A_g state with its origin near 17 230±100 cm⁻¹. This corresponds to a ¹B_u−¹A_g energy gap of 3470±100 cm⁻¹, and may help account for the nonfluorescence of β‐carotene.