Assignments of the [formula omitted] singlet states of p-benzoquinone

Abstract

The vapor phase fluorescence spectra of p-benzoquinone- h 4 and d 4 are reported and discussed in relation to the assignment of the low lying singlet states. The low temperature, polarized single crystal electronic absorption spectra of p-benzoquinone and several of its isotopic derivatives are reported. From the isotope shifts and band polarizations of the various vibronic origins, a detailed vibronic analysis is offered of the electronic absorption spectrum of p-benzoquinone which indicates a near degeneracy of the 1 A u and 1 B 1 g electronic states.