Ab Initio Potential Surfaces of BeH2+

The potential surface of the BeH₂⁺ molecular ion in $C_{\text{2υ}}$ geometries is computed by two ab initio methods: self‐consistent‐field (SCF) theory and valence bond configuration interaction (VBCI). Both calculations predict this ion to be weakly bound in a ${}^2{A}_1$ state. A bound excited state of ${}^2{B}_2$ symmetry is also predicted. According to SCF theory, the ${}^2{A}_1$ state has a binding energy relative to H₂ and ${\text{(1s}}^2{\text{2s)}}^{2}S{\mathrm{Be}}^{+}$ of 0.19 eV, a BeH distance of 4.43 bohr, and a HBeH angle of 19.9°. The ${}^2{B}_2$ state has a binding energy relative to H₂ and (${\text{1s}}^2{\text{2p)}}^{2}P{\mathrm{Be}}^{+}$ of 3.2 eV, a BeH distance of 2.63 bohr, and a HBeH angle of 73.1°. SCF theory also gives an approximate ionization energy for BeH₂ of about 9.71 eV. According to the VBCI calculation, the ${}^2{A}_1$ state has a binding energy of 0.11 eV, a BeH distance of 4.16 bohr, and a HBeH angle of 20.5°, while the ${}^2{B}_2$ state has a binding energy of 2.74 eV, a BeH distance of 2.76 bohr, and a HBeH angle of 93°. These ab initio results plus some experimental data for related ions strongly indicate that BeH₂⁺ exists in two stable states which should be observable in mass spectrometers.