Determination of highly excited states of diatomic-molecular ions using exact H2+-like orbitals.

Abstract

A simple configuration-interaction method to calculate accurate electronic energies of two-electron molecular ions at intermediate internuclear distances is presented. The correlated basis functions are constructed from exact ${\mathrm{H}}_{2}^{+}$ molecular orbitals, and include an explicit dependence on the interelectronic distance in order to describe the cusp conditions of the Coulombic field. An important simplification of the Hamiltonian matrix elements is deduced. The method is applied to determine new potential curves of highly excited states of ${\mathrm{He}}_{2}^{2+}$ molecular ions dissociating into two excited fragments. The $^{1}\mathrm{\ensuremath{\Sigma}}_{\mathit{g}}$ state dissociating into ${\mathrm{He}}^{+}$(2p)+${\mathrm{He}}^{+}$(2p) presents a deep well located at R=5.0 a.u., where metastable states can survive. These states could be of interest in excimer lasers.