EXPERIMENTAL-EVIDENCE TO RYDBERGIZATION OF ANTIBONDING MOLECULAR-ORBITALS

Experimental evidence is presented for the process of molecular orbital Rydbergization postulated by Mulliken, whereby an antibonding orbital continuously changes its character from predominantly Rydberg to predominantly valence on its way to dissociation. By matrix-isolation spectroscopy of the A B-1(1) state of H2O in Ar and Kr matrices and in ice, we show that the absorption threshold behaves like a valence transition while the maximum has a behaviour typical of Rydberg transitions in condensed matter, in agreement with the predicted changing character of the state.