Physics Journal of the Indonesian Physical Society
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THE CLOSECOUPLING FORMALISM USING THE L^{2} BASIS TO THE ELECTRONHELIUM FUNCTIONS
A. Kartono^{1} and T. Winata^{2}
^{1}Laboratory for Physics of Electronic Material, Physics Department, Faculty of Matematical and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia ^{2}Physics Department, Faculty of Matematical and Natural Sciences, Institut Pertanian Bogor, Jl. Raya Pajajaran, Bogor 16143, Indonesia
Abstract
The closecoupling formalism is studied by expanding the target states in nonorthogonal L^{2} Laguerre basis. The target atom is studied using frozencore approximation where one of the electrons is restricted to be in the 1s He^{+} orbital. The frozencore approximation reduces convergence studies to treating only one electron excitation. By separating the variables related to the electron positions, the helium states can then be written as a coupling between two single electron states where each state can be expressed as L^{2} basis expansion. The eigen energies and states are then obtained by diagonalizing the frozencore Hamiltonian system in a L2 basis. The closecoupling formalism where the L^{2}target states can be inserted are also discussed.
