Doubly excited nonautoionizing P, D, and F states of helium with Coulomb and screened Coulomb potentials

We have investigated the doubly excited P-1,3(e), D-1,3(o), and F-1,3(e) nonautoionizing states of helium atom with Coulomb and screened Coulomb (Yukawa) potentials in the framework of Ritz variational principle. Highly accurate correlated exponential wave functions with exponents generated by a quasirandom process are used to represent the correlation effect. For the Coulomb case, the metastable bound-excited 2pnp P-1(e) (3 < n < 5), 2pnp P-3(e) (2 < n < 5), 2pnd D-1,3(o) (3 < n < 9), and 2pnf F-1,3(e) (4 < n < 9) states energies are reported. Our upper-bound results for the 2pnd D-1(o) (3 < n < 7), 2pnf F-1(e) (4 < n < 8), D-3(o) and F-3(e) states are the lowest values up to this date. For the screened Coulomb case, the lower-lying metastable bound states energies for different screening parameters and for each spin states are also reported.