Strong nondipole effects in low-energy photoionization of the 5s and 5p subshells of xenon

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 nondipole parameter g5s exhibits a dispersion-curve variation near the first minimum of the 5s cross section at 35 eV, reaching a minimum value of 20.8 near 40 eV. Rapid variation of g5s is also found near the second minimum of the 5s cross section at 150 eV, where g5s reaches a maximum value of 1.2. Smaller, but significant, nondipole effects are also found in the parameter z5p5g5p13d5p , 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 g5s and z5p 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.