One-Center Wavefunction for the Ground State of the HeH+ Molecular Ion

The HeH+ molecular ion is a member of that class of diatomic hydride molecular ions which are one-center systems at R=0 and at R=∞. The total electronic energy of the ground state of HeH+ has been calculated over a wide range of R with a 30-term orbital product wavefunction centered on the helium nucleus. The results are compared with a James and Coolidge-type calculation and with a two-center orbital product calculation. The results in the order Evett, Anex, and present calculation are Re=1.432, 1.446, 1.464 a.u.; ωe=3600, 3378, 3184 cm—1; and E(R=1.4 a.u.)=—2.9730, —2.9742, —2.9691 a.u. The energy of the present calculation is the lowest for R greater than about 2 a.u. and is lower than the classical polarization energy for 2<R<4 a.u. For R>4 a.u. the one-center interaction energies [E(R)—E(∞)] lie quite close to the classical polarization energies.