Angular distribution of photoelectrons of Xe5pspin-orbit components between 20 and 105 eV

With the use of synchrotron radiation, the $\beta$ parameters of the Xe $5p$ components have been measured between 20 and 105 eV in a regime in which both relativistic and many-body effects are important. The experimental $\beta$ values of ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ are found to be in good accord with the relativistic random-phase-approximation (RRPA) theory, but only in fair agreement with the Dirac-Fock prediction. Similarly, the branching ratio $\sigma \frac{\left({}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}\right)}{\sigma \left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)}$ agrees well with the RRPA. However, the Dirac-Fock model accounts satisfactorily for the difference in the $\beta$ values of the components indicating similar many-body effects acting on both components. A brief description is given of the new gas-phase angle-resolved electron-spectrometry system used in this work.