OPTICAL OPTICAL DOUBLE-RESONANCE SPECTROSCOPY OF CL2 - ANALYSES OF THE 0U-3(2)) ION-PAIR STATES(, 1U, AND 2U(P)

The optical-optical double-resonance spectroscopy is applied to study the ion-pair states of Cl2 correlating to Cl-(1S) + Cl+(P-3(2)). In th e (1 + 2) photoexcitation sequence, we gain access to the 0u+(P-3(2)) and 1u(P-3(2)) ion-pair states through the A3PI(1u) and B3PI(0u+) stat es as intermediates. These states are found to lie closely together an d show strong heterogeneous coupling with each other. The transitions to the nearby 2u(P-3(2)) state are first noticed as extra lines throug h the mixing with the 1u(P-3(2)) state, and the observations are exten ded by the perturbation-facilitated optical-optical double-resonance t echnique. The energy levels of the 0u+, 1u, and 2u(P-3(2)) states are analyzed in detail by including the heterogeneous interaction between these states. The electronic structures of the ion-pair states are dis cussed. These results allow us to map out the ion-pair states and to c lear up the puzzle of previously observed states in the 7-eV region. ( C) 1994 Academic Press, Inc.