Ritz variational calculation for two-electron–one-photon transitions in helium

摘要

Variational calculations for the energy levels of doubly excited 3dnf (~(1,3)D°) states (n=4-12) for helium have been performed using the extended Hylleraas basis set. No previous calculations for the energy eigenvalues for the 3dnf (~(1,3)D°) states for (n =7-12) exist. Prediction of two-electron–one-photon peaks at 12.220, 12.649, 12.859, 12.978, 13.054, 13.110, 13.141, 13.168 and 13.213 eV corresponding to the transitions 2p~2 (~3P~e)→3dnf (~3D°) (n=4-12), respectively, is reported here. Highly precise energy eigenvalues of doubly excited 2pnd states (~(1,3)D°) (n=3-8) for helium are also reported and the upper bound energies are the lowest yet obtained. The effective quantum numbers (n~*) of the above mentioned states are calculated using quantum defect theory.