Guillemin—Zener Energy of H2+

The energy of the H2+ ground state 1sσ calculated with the Guillemin—Zener approximate wavefunction, ψs=Nsexp(−Raλ/2) cosh(Rbμ/2) lies within 0.0005 e2/a0 of the exact for the full range of internuclear separations. In the limit of zero separation, ψs=Nsexp(−rA−rB) cosh[(rA−rB)/3]. The energy still lies within 0.0010 e2/a0 when the additional requirement is imposed that Hψs remains finite at the nuclei. The Guillemin—Zener energy is less accurate for the first excited 2pσ state.