Time Delay in the Photoionization of Xenon: Relativistic Effects

Owing to the advent of attosecond pulses of ioning radiation, it has been possible to measure the time delay between various photoionization channels in atoms; a number of theoretical calculations have also been performed. However, none of the extant studies have included relativistic interactions. In this study, time delay in the 5s$\to \varepsilon $p$_{1/2}$,$\varepsilon $p$_{3/2}$, in 5p$_{3/2}\to \varepsilon $d$_{5/2}$, $\varepsilon $d$_{3/2}$, $\varepsilon $s$_{1/2}$ and in 5p$_{1/2}\to \varepsilon $d$_{3/2}$, $\varepsilon $s$_{1/2}$ dipole photoionization channels in Xe have been calculated within the framework of the Wigner-Eisenbud formalism [1,2] using the relativistic random phase approximation (RRPA) [3]. The RRPA includes major electron correlations which play an important role in influencing the time delay. Further, the RRPA includes relativistic effects \textit{ab initio} and is thus especially suited for determining the time delay in spin-orbit split relativistic dipole channels. New effects, due to relativity, are found in the neighborhood of Cooper minima.\\[4pt] [1] E. P. Wigner, Physical Review 98, \textbf{145} (1955).\\[0pt] [2] L. E. Eisenbud, Ph. D. thesis, Princeton Univ. (1948).\\[0pt] [3] W. R. Johnson and C. D. Lin, Physical Review A \textbf{20}, 964 (1979).