TheE,Fthinsp;1Sgr;+gdoublehyphen;minimum state of hydrogen: Twohyphen;photon excitation of inner and outer wellsa)

摘要

Lowhyphen;lying vibrational levels (v=2 and 3) of the outer well of the doublehyphen;minimumE,Fthinsp;1Sgr;+gstate of molecular hydrogen are experimentally observed for the first time permitting a rotational analysis. TheE,Fstate is excited by twohyphen;photon absorption using tunable (sim;195 nm) Ramanhyphen;shifted radiation of a frequencyhyphen;doubled dye laser. The nonlinear absorption is detected by monitoring the subsequent photoionization of theE,Fstate. Homogeneous perturbations are observed between thevE=1 andvF=2 levels of the inner and outer wells, respectively. The molecular parameters for these levels (derived by a deperturbation analysis) as well as those for the unperturbedvF=3 level are compared with recentab initiocalculations and small deviations are noted. The rotational intensity distribution of theEndash;X(0,0) band mirrors the ground state rotational population, whereas the corresponding distributions of theEndash;X(1,0) and (2,0) bands as well as theFhyphen;X(4,0) band do not follow this pattern. This is interpreted in terms of vibronic coupling between the inner and outer wells of theE,Fstate. A comparison between the experimental rotationless intensities and those calculated fromab initioground and excited state vibrational wave functions suggests that photoionization from the outer well is more effective than from the inner well.