The¹P^oresonant states of LiII between the N = 2 and 3 thresholds

Abstract

Abstract. We studied the lowest five doubly excited 1 P o resonant states of Li + between the N=2 and 3 thresholds by the saddle-point complex rotation method with B-spline functions. The doubly excited states are grouped in Rydberg series labeled by the quantum numbers K, T, A. Our results of energies and widths are in good agreement with other theoretical and experimental results. IntroductionDoubly excited states of two-electron atom and ions have attracted physicists to study experimentally and theoretically. The doubly excited 1 P o resonant states of Li + have been observed firstly by Dual Laser Plasma technique [1]. They were also studied experimentally by beam-foil techniques [2,3], and using the ejected electron spectroscopy method [4]. After high-resolution monochromators at synchrotron-radiation facilities have been developed, highresolution measurements on Li + ion were performed at the Advanced Light Source [5] and Super-ACO [6]. Diehl et al [6] have measured the doubly excited states of Li + below n=2 threshold. More recently, absolute cross-section measurements for the double photoexcitation of Li + ion have been performed by using the photo-ion merged-beam endstation. Accurate measurements on several members of the 1 P o Li + ( 2 (0,1) + n , 3 (1,1) + n ) ion have been made [7,8,9]. On the theoretical side, some resonances have been studied by the complex rotation method [10], the diagonalization approximation [11], the pseudo-potential-Feshbach method [12], the saddle-point complex-rotation method [13],the variation method with combining Hylleraas and incomplete hydrogenic wave functions [15], the density-functional method [14], the R-matrix method [7,8,9] , the saddle-point complex rotation method [16], and the SCUNC method [17].