POLARIZABILITIES OF THE FIRST EXCITED (A(1)DELTA(G)) AND GROUND (X-3-SIGMA(-)(G)) STATES OF MOLECULAR-OXYGEN

Ab initio computational methods have been employed to determine the fr equency-dependent polarizabilities of both the first excited (a(1)Delt a(g)) and ground (X(3)Sigma(g)(-)) states of molecular oxygen. Polariz abilities are reported for oxygen in the gas phase as well as under bo th equilibrium and nonequilibrium conditions in four solvents. The dat a consistently show that, for any set of comparable solvation conditio ns, the polarizability of O-2(a(1)Delta(g)) is smaller than that of O- 2(X(3)Sigma(g)(-)). This phenomenon differs from that observed with mo st other molecules, where the polarizability of the excited state is t ypically much larger than that of the ground state. The results reflec t unique changes in the orbital occupancy associated with electronic e xcitation in the oxygen molecule. The consequences of this finding are important, particularly with respect to the interpretation of the sol vent effect on radiative transitions in oxygen.