Strong nondipole effects in low-energy photoionization of the 5s and 5p subshells of xenon -: art. no. 022504

Large nondipole effects are predicted in the angular distribution of photoelectrons from the 5s and 5p subshells of xenon for photon energies below 200 eV. The nondipore parameter gamma (5s) exhibits a dispersion-curve variation near the first minimum of the 5s cross section at 35 eV, reaching a minimum value of -0.8 near 40 eV. Rapid Variation of gamma (5s) is also found near the second minimum of the 5s cross section at 150 eV, where gamma (5s) reaches a maximum value of 1.2. Smaller, but significant, nondipole effects are also found in the parameter zeta (5p) = gamma (5p) + 3 delta (5p), which has a maximum value of 0.15 near 50 eV, and a second maximum value of 0.18 near 160 eV. The higher energy maxima in gamma (5s) and zeta (5p) arise from correlation enhanced by shape resonances in the 4p --> f quadrupole photoionization channels. These predictions are based on relativistic random-phase approximation calculations in which excitations from 5p, 5s, 4d, 4p, and 4s subshells are coupled.