On the calculation of C4(+) (4, 4) doubly excited states

We study S-1(e)(4, 4) and D-1(e)(4, 4) resonant states of C4+. Some differences between the widths obtained in Feshbach and complex-scaling approaches are analysed in detail in the case of S-1(e)(4, 4) resonances. We show that, for C4+(4, 4) states located below the N = 3 threshold, the complex-scaling approach gives the perturber parameters when developed in small basis sets. This paper illustrates the relation between the concept of autotransfer to Rydberg states, proposed recently in the collisional context, the quantum defect theory and the complex-scaling approaches.