Systematics of Rydberg structure in the spectra of the rare gas dimers between the atomic 2P/sup o//sub 3/2/ and 2P/sup o//sub 1/2/ fine-structure thresholds

The relative photoionization cross sections for the rare gas dimers Ar2, Kr2, and Xe2 were measured in the energy region between the respective atomic 2P/sub 3/2//sup o/ and 2P/sub 1/2//sup o/ fine-structure thresholds at wavelength resolutions of 0.15 A for Ar2, 0.28 A for Kr2, and 0.45 A for Xe2. Discrete autoionization structure was observed for all three systems and has been partially analyzed in terms of Rydberg series converging to the C 2Pi/sub 1/2u/ state of the molecular ions. Vertical binding energies for the individual Rydberg states were estimated based on the assumption that the Rydberg states dissociate to a rare gas atom in an ns'[1/2]1/sup o/ or nd'[3/2]1/sup o/ excited state plus a rare gas atom in the 1S0 ground state. The binding energies thus obtained are in excellent agreement with the corresponding values for the C 2Pi/sub 1/2u/ ionic states obtained from previously reported photoelectron spectra. Some of the molecular structure exhibits Beutler--Fano profiles similar to those observed in the nd'[3/2]1/sup o/ atomic series. This is in contrast to the energy region near the first ionization threshold, where it is extremely difficult to find a simple correlation between the atomic and molecular Rydberg structure