R-matrix calculation of the photoabsorption of KII, CaIII and ScIV

The R-matrix approach is employed to study the photoionization of the argon -like ions K II, Ca III and Sc IV. The 3s3p(6)np P-1 degrees Rydberg series is identified for each ion. Excellent agreement with previously published resonance positions is observed but the q-reversal reported for Cam by van Kampen et al is not replicated in this calculation. Good agreement with exp erimental data is observed for K II but not for Ca III. The differences in shape of the total cross sections along the sequence are attributed to the relative positions of the 3s and 3p Cooper minima.