RESONANT 2-COLOR DETACHMENT OF H- WITH EXCITATION OF H(N = 2)

The cross sections for resonant two-color, two-photon detachment of H- with excitation of the degenerate H(2s) and H(2p) levels are calculat ed within a semiempirical adiabatic hyperspherical representation. The first photon, with energy omega1 = 0.4017 a.u., is resonant with the well-known Feshbach P-1(0) resonance below the H(n = 2) threshold. The second photon, with energy omega2 greater-than-or-equal-to 0.12605 a. u., scans the energy region above the H(n = 2) threshold over which lo ng-range dipole-field-induced cross-section oscillations are predicted to occur. Such Gailitis-Damburg oscillations have not yet been observ ed experimentally. Results for various pairs of light polarization for the two photons are presented. Our resonant two-color, two-photon det achment cross sections are 8-9 orders of magnitude greater than the co rresponding nonresonant, single-color, two-photon detachment cross sec tions obtained by Liu, Du, and Starace [Phys. Rev. A 43, 5891 (1991)]. Unmistakable evidence of long-range dipole-field effects is presented over the 5-meV energy range above the H(n = 2) threshold. Furthermore , the differential cross sections for right- and left-circularly polar ized, copropagating photons and especially the circular dichroism diff erential cross sections are shown to have nearly a full cycle of a gre atly enhanced dipole-field-induced oscillation extending over the regi on from threshold to almost-equal-to 34 meV above.