Strong electric-field effects on the doubly-excited intrashell states of He below the He+(N = 2) threshold

The method of complex-coordinate rotation is used to investigate electric-field effects on the doubly-excited 2s2p ¹P⁰, 2p^{2 1}D^e, 2p^{2 3}P^e and 2s2p ³P⁰ states of He. Strong electric-field strengths up to F=0.02 Ry are used in our present study. Products of Slater orbitals are used to represent the two-electron wave functions, with l_max=8 being employed for the individual electron. Block matrices with up to L_max=5 (H-states) are used to investigate the convergence behavior for the resonance parameters (resonance energy and width). When the external electric field is turned on, "classic" Stark effect is observed for the M=0 and M=ǃ components of the two singlet-spin states and for the M=ǃ components of the triplet-spin states. Comparisons are made with other calculations when available.