R-matrix with Intermediate Coupling Frame Transformation Calculation of the Spin-Orbit Interactions in Ar Photoionization*

Motivated by the recent observation of the giant spin orbit interactions in Ar photoionization [1], we have performed a highly-correlated R-matrix multichannel quantum defect theory (MQDT) along with a term-coupled LS-JK frame transformation method to account for fine structure effects. Briefly, it was found in [1] that the cross sections for the LS forbidden $3p^4[^3P]4p$ $^4D^o_{1/2}$ and $3p^4[^3P]4p$ $^4D^o_{3/2}$ states were 16 to 30 times larger than those for the LS-allowed doublet states, indicating strong relativistic effects. A comparison of the experimental results with our LS and $LS-JK$ frame transformation R-matrix calculations will be presented and the nature of the effects responsible for the observed spectra elucidated. \begin{enumerate} \bibitem{1} D. H. Jaecks, O. Yenen, K. W. McLaughlin, S. Canton, J. D. Bozek and M. Downsbrough, Phys. Rev. A {\bf 70}, 040703(R) (2004). \end{enumerate}