Polarizations of the Low-Energy Sn←S Transitions in 9,10-Anthraquinone

Abstract

The polarizations of the transitions to the lowest n—π* and three π—π* singlet states of 9,10-anthraquinone have been measured relative to that of the phosphorescence by the method of photoselection. Assuming that the n—π* and two π—π* transition moments lie in the molecular plane and utilizing the previous result that the T1←S0 transition moment is parallel to the carbonyl axes (Z), the n—π* absorption is found to be polarized along Y and the first three π—π* transitions along Y, Z, Y, respectively. Y is the axis in the molecular plane perpendicular to the carbonyl axis. The ordering of the π* states is compared with the predictions of the two available SCF calculations and with the predictions of the Platt spectroscopic moment theory.