Laser bandwidth effect on photoelectron angular distribution for resonant two-photon autoionization of H2

Abstract

In this two-photon process, the H2 molecule is excited from the ground vibrational level (v g = 0; j g = 0) of the x′Σ g state to different vibrational levels (v i = 0,1,2, j i = 1) of the B′Σ u state and thereafter either to the lowest autoionizing state of ′Σ g (1σu2) symmetry or directly to the ionization continuum ( H 2 + : x 2 Σ g ; v l = 0,1, 2; j l = 0). Energy of the autoionizing state is −0.4632 a.u., which corresponds to the turning point R = 2.4 a.u. The wavelengths required for the above transitions are 1100 and 1500 Å, respectively. Resolvent operator technique has been used to obtain photoelectron (PE) angular distribution.1,2 The laser bandwidth (γ L ) has been found to have different spectacular effects on PE angular distribution depending on laser intensities and also on the relative magnitude of the bandwidth compared to the spontaneous decay width (γ a ) of the intermediate resonant state. Moreover γ L affects the PE angular distribution differently for transitions combining different intermediate (v i , j i ) and final vibrational levels (v l , j l ). Significant departure from the usual feature [≈1 + βP2(cosθ)] for PE angular distribution was noticed for larger bandwidths.