Photoionisation of K²⁺using R-matrix theory

The authors have calculated the 3p photoionisation cross section of K 2+ (isoelectronic series of Cl, with ground-state configuration 3p 5 ) using R-matrix theory. The results of two calculations, one involving a 3d pseudo-orbital, are compared with the authors' previous ones beyond the 3p 4 1 S e threshold, and, for the first time, various families of autoionisation resonances are pointed out and analysed in terms of Fano's parameters and quantum defects. This analysis concerns Rydberg series converging on the 1 D e and 1 S e thresholds, since they describe the residual ion K 3+ (3p 4 ) from its lowest three terms: 3 P e , 1 D e and 1 S e .