Resonance Profiles of Mg 3pns Autoionizing States

Multichannel quantum-defect theory is combined with the R-matrix calculations to study the resonance lineshape of autoionizing 3pns state of atomic magnesium. The R-matrices calculated with different reaction volumes hardly affect the total cross section of photoionization of the Mg 3sns Rydberg state. The comparison between theoretical and experimental results fs furnished.