Complex-scaling of screened Coulomb potentials for resonance calculations utilizing the modified Bessel functions

The screened Coulomb potential (SCP) has been extensively used in atomic physics, nuclear physics, quantum chemistry and plasma physics. However, an accurate calculation for atomic resonances under SCP is still a challenging task for various methods. Within the complex-scaling [1] computational scheme, we have developed a method utilizing the modified Bessel functions to calculate doubly-excited resonances in two-electron atomic systems with configuration interaction-type basis. To test the validity of our method, we have calculated $S$- and $P$-wave resonance states of the helium atom with various screening strengths, and have found good agreement with earlier calculations using different methods [2, 3]. Our present method can be applied to calculate high-lying resonances associated with high excitation thresholds of the He$^{+}$ ion, and with high-angular-momentum states. The derivation and calculation details of our present investigation together with new results of high-angular-momentum states will be presented at the meeting.\\[4pt] [1] Y. K. Ho,\textit{ Phys. Rept. }\textbf{99}, 1 (1983), and references therein;\\[0pt] [2] S. Kar and Y. K. Ho, \textit{Phys. Rev. A} \textbf{72}, 010703 (2005);\\[0pt] [3] S Chakraborty and Y. K. Ho, \textit{Eur Phys. J. D} \textbf{49}, 59 (2008)