Journal of Theoretical and Computational Studies
THE CLOSE-COUPLING FORMALISM USING THE L2 BASIS TO THE ELECTRON-HELIUM FUNCTIONS
A. Kartono1 and T. Winata2
1Laboratory for Physics of Electronic Material, Physics Department, Faculty of Matematical and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia
2Physics Department, Faculty of Matematical and Natural Sciences, Institut Pertanian Bogor, Jl. Raya Pajajaran, Bogor 16143, Indonesia
The close-coupling formalism is studied by expanding the target states in non-orthogonal L2 Laguerre basis. The target atom is studied using frozen-core approximation where one of the electrons is restricted to be in the 1s He+ orbital. The frozen-core 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 L2 basis expansion. The eigen energies and states are then obtained by diagonalizing the frozen-core Hamiltonian system in a L2 basis. The close-coupling formalism where the L2-target states can be inserted are also discussed.