T. Banerjee

Theoretical and experimental demonstrations of the existence of quadrupole Cooper minima

Calculations and measurements of the Xe 5s and 5p nondipole photoelectron asymmetry parameters are obtained, which present clear evidence of the existence of quadrupole Cooper minima, i.e., minima in quadrupole matrix elements as a function of energy, in the photoionization process. This verifies earlier predictions of quadrupole Cooper minima.

Resonance-induced deviations of β from 2.0 for rare gas s-subshell photoionization

We investigate the case of resonance-induced deviations of the angular distribution anisotropy parameter, β, from its nominal value of 2.0 for the Kr 4s-subshell at the 3d → mp(m ≥ 5) excitations and the Xe 5s-subshell in the region of the 4d → mp(m ≥ 6) excitations. We observe small but unmistakable variations of β from 2.0 at these resonances. In the case of Kr the largest deviation from 2.0 is a mere −0.030(6), β4s = 1.970(6), while in Xe it is definitively larger at −0.080(6), β5s = 1.920(6). To understand these results in more detail, we have carried out relativistic random phase and relativistic multi-channel quantum defect calculations. Our theoretical results clearly indicate deviations of β from 2.0 for these photolines in these resonance regions, although the degree of variation is predicted to be larger than what is observed.

Wigner time delay in quadrupole photoionization channels of atomic Hg

Time delay in quadrupole (E2) channels is studied in atomic Hg using the Relativistic Random Phase Approximation. Interchannel coupling is found to be extremely important and large time delays are found in the region of quadrupole (E2) Cooper minima.

Multiple Cooper minima in ground state E2 photoionization of high Z atoms

Quadrupole photoionization from valence and intermediate subshells of atomic mercury, radon and radium have been studied in the present work. Multiple Cooper minima in the E2 channels have been found even when only intra-shell inter-channel coupling is included, in contrast with the dipole case in which multiple Cooper minima were found only when inter-shell interchannel coupling was included.

Dipole and Quadrupole Photoionization of Intermediate Subshells of Atomic Mercury

Dipole and quadrupole photoionization parameters for intermediate subshells of mercury have been studied using the relativistic-random-phase-approximation (RRPA). Multiple Cooper minima are observed in 5d quadrupole cross sections, even at the level of intrashell coupling. It has been found that the effect of interchannel coupling is much more significant for dipole photoionization parameters than for quadrupole parameters.