Exponentially correlated Hylleraas‐configuration interaction studies of atomic systems. II . Non‐relativistic energies of the 1 through 6 states of the Li ⁺ ion

The exponentially correlated Hylleraas‐configuration interaction wave function (E‐Hy‐CI) is a generalization of the Hylleraas‐configuration interaction (Hy‐CI) in which the single of an Hy‐CI wave function is generalized to the generic type . This type of correlation has the right behavior both in the vicinity of the cusp and as goes to infinity; this work shows that wave functions containing both linear and exponential factors converge more rapidly than either one alone for low‐lying excited states of 1 S symmetry. E‐Hy‐CI variational calculations with up to 8568 configurations lead to a nonrelativistic energy of −7.2799 1341 2669 3059 6491 6759 hartree for the 1 1 S ground state of the Li+ ion.