Radial and angular correlations in doubly excited states: A time-dependent perturbation approach

✍ Scribed by A. K. Das; T. K. Ghosh; D. Ray; T. K. Mukherjee; P. K. Mukherjee

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 145 KB
• Volume: 76
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(2000)76:1<99::aid-qua9>3.0.co;2-j

✦ Synopsis

The time-dependent variation perturbation theory TDVPT was applied to estimate separately the effect of radial and angular correlations in the doubly excited states of two-electron systems. Test calculations were performed for the transitions 2 1 e 2 1 e y 2 1 e 2 1 e Ž .

q 2q

1 s : S ª 2 s : S for H and 1 s : S ª ns : S ns 2, . . . , 5 for He, Li , Be , and B 3q . Transition energies to various doubly excited states were estimated using radially correlated basis sets as well as with basis sets which take care of both radial and angular correlations. Angular correlation is taken care of by incorporating higher angular momentum basis sets in the expansion of the perturbed wave functions. The excitation energy is lower in all the cases, indicating the correct behavior. Overall improvement of the results is observed when angular correlation is included. The effect of angular correlation, however, diminishes rapidly with increase of the nuclear charge. This has been demonstrated explicitly for the lowest doubly excited transitions in the highly stripped ions Al 11q , Si 12q , P 13q , S 14q , and Cl 15q .