The singlet nπ* states of para-benzoquinone

The vibronic nπ* singlet spectra of p-benzoquinone-h₄ and p-benzoquinone-d₄ have been observed in a supersonic jet and some as yet unknown excited state fundamentals in the vapor phase have been assigned. The electric dipole forbidden, magnetic dipole allowed origin of the ¹B_1g ← ¹A_g transition is observed at 20045 cm^?1. The origin of the¹A_u ← ¹A_g, transition has been indirectly determined at 19991 cm^?1 from the vibronic excitation spectra. Neither shows a deuterium shift.