Stark effects on the low energy electronic states of p-benzoquinone single crystals

Abstract

The Stark effect on the visible absorption spectra of p-benzoquinone single crystals has been measured using modulation techniques. The measurements of second order Stark effects confirm the presence of at least two close lying electronic nπ* states in both the singlet and triplet systems. Both the origin of the first singlet-singlet and singlet—triplet transition appear as doublets separated by 3.5 and 18 cm−1, respectively. For the triplet state the low energy component is Stark induced and has not been observed previously in absorption. The doublet components are mixed in the electric field showing that they are of different parity. They are tentatively assigned as inversion doublets of a symmetric double well potential produced by the vibronic interaction of two different electronic nπ* states.