Related to "Asymmetry" function for Radiative recombination process

[pritivish]

Dear All,

In FAC, the "Asymmetric" function is used to calculate the photoionization asymmetry parameters for given relativistic subshells.
I want to know that how it ("Asymmetric") exactly calculates the RR cross-sections in perpendicular and parallel directions. I did not found any reference or theory in the manual or source paper.

** Mainly, I want to know the reference from where theory is adopted for this "Asymmetry" function **