TOWARD THE UNDERSTANDING OF HE-2(-) EXCITED-STATES

Using a recently developed state-specific method for the calculation of wavefunctions of diatomic molecules (N.C. Bacalis, Y. Komninos and C.A. Nicolaides, Phys. Rev. A 45 (1992) 2701), we calculated the potential energy curve for a localized wavefunction of a (4) Phi(g)(1 sigma(g)(2)1 sigma(u)2 pi(u)1 delta(g)) state in He-2(-), including electron correlation. This state is a Feshbach resonance, lying below its parent He-2 (3) Pi(g)(1 sigma(g)(2)1 sigma(u)2 pi(u)) and (3) Delta(g)(1 sigma(g)(2)1 sigma(u)1 delta(g)) exicted states and autoionizing into the continuum of He-2 (3) Pi(g)(1 sigma(g)(2)1 sigma(u)1 pi(u)) by the two-orbital rearrangement 2 pi(u)1 delta(g) --> 1 pi(u) epsilon delta(g) or 1 pi(u) epsilon gamma(g) (in (s)igma, pi, delta, phi, gamma...diatomic notation). From our state-specific numerical Hartree-Fock calculations it can be concluded that the localized solution for the I-4(g)(1 sigma(g)(2)1 sigma(u)1 delta(g)1 phi(u)) state obtained by L. Adamowicz and T.P. Pluta (Chem. Phys. Letters 179 (1991) 517), should give rise to a shape resonance above the lowest He-2 (3) Delta(u)(1 sigma(g)(2)1 sigma(u)1 delta(g)) state.