Photoelectron angular distribution and linear magnetic dichroism in the $4p$ photoemission from Rb atoms

The angular distribution of photoelectrons and linear magnetic dichroism in the angular distribution for the $4p$ photoemission from Rb atoms in the ground state, oriented by laser pumping, were measured in the photon energy range from $50$ to $100$ eV. The experimental results are compared with the multiconfiguration Dirac-Fock (MCDF) calculations. We show that the zero-crossing of the dichroism as a function of energy is connected with the Cooper minimum in the cross section. This fact can be used for an accurate determination of the position of the Cooper minimum.

Figure 1

The part of the experimental $4p$-photoemission spectrum of Rb studied (solid curve). Lines 1 and 2 are assigned as $4p_{3/2}^{-1}5s$ with $J_f=2$ and $1$, respectively, lines 3 and 4 belong to the ionic multiplet $4p_{1/2}^{-1}5s$ $J_f=0$ and $1$, respectively. Line 5 is attributed to the configuration $4p^{-1}4d$. The bars represent the theoretical spectrum calculated within the MCDF approach. For more details see the text.

Figure 2

Angular anisotropy parameter $\beta$ as a function of photon energy for the $4p$ photoionization of the ground state of the Rb atom with transition to the $4p^5({}^2{P}_{3/2})5s[3/2]{}_2$ (line 1) and $4p^5({}^2{P}_{3/2})5s[3/2]{}_1$ (line 2) states of Rb${}^{+}$ ion. The curves show the calculated results. The experimental data are shown by symbols with error bars.

Figure 3

(a) The experimental $4p$-photoelectron spectrum from the Rb ground state pumped by right (black curve) and left (gray curve) circularly polarized laser light, measured at the photon energy of 60 eV. (b) The corresponding theoretical spectra.

Figure 4

Relative LMDAD as a function of photon energy for the two final ionic states $4p^5({}^2{P}_{3/2})5s[3/2]{}_{2,1}$ (lines 1 and 2). Curves represent the results of calculations, points with error bars show the experimental data.