Interaction Energy of an Alkali Metal with a Rare Gas

A molecular orbital self-consistent field calculation is made for closed shell ions, LiHe+ and LiHe— as function of internuclear distance. The eigenfunctions obtained from these calculations were used to calculate the potential energy curves for the neutral Li–He. This system has some interesting properties. For example, these calculations suggest the probable quenching of certain excited states of an alkali metal when in close interaction with a rare-gas atom. All of the curves obtained are repulsive except for the LiHe+ curve which has a shallow minimum and follows an expected 1/r4 attractive potential. Fair values are obtained for the ionization energies of the Li and He atoms and the electron affinity of Li. These calculations indicate that open-shell systems with few electrons can be treated by making the simpler SCF calculation on a closely related closed-shell system and using the resulting eigenfunctions to calculate the energy of the closed shell system.