Σ + 7 and Π7 states of manganese hydride

Abstract

Ab initio self‐consistent‐field calculations have been carried out close to the Hartree‐Fock limit for the high spin ${}^7{\Sigma }^{+}$ and ${}^7\Pi$ electronic states of MnH. Five different hydrogen‐centered basis sets of Slater functions are tested for H⁻ and MnH. Predicted spectroscopic constants (with experimental values in parentheses) for the ${}^7{\Sigma }^{+}$ ground state are $D_e\text{=1.57\hspace{0.17em}}\mathrm{eV}{\text{\hspace{0.17em}(2.4 ± 0.3), ω}}_e\text{=1549\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\text{\hspace{0.17em}(1548), r}}_e\text{=1.780\hspace{0.17em}}\mathrm{\AA }\text{\hspace{0.17em}(1.722),\hspace{0.17em}}\mathrm{and}{\mathrm{\hspace{0.17em}B}}_e\text{=5.32\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}\text{\hspace{0.17em}(5.68)}$ . And for the ${}^7\Pi$ state, $T_e\text{= 21\hspace{0.17em}870\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\text{\hspace{0.17em}(17\hspace{0.17em}700), ω}}_e\text{=1708\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\; r}}_e\text{=1.703\hspace{0.17em}}\mathrm{\AA }\mathrm{,\hspace{0.17em}}\mathrm{and}{\mathrm{\hspace{0.17em}B}}_e\text{=5.88\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}\text{\hspace{0.17em}(6.43)}$ . The electronic structure of the two states is discussed with respect to the contributions of the different molecular orbitals to the electric dipole moment and population analysis. Although the population analysis predicts the ${}^7{\Sigma }^{+}$ state to be more ionic than the ${}^7\Pi$ state, the dipole moments are computed to be 1.6 and 4.1 D, both +MnH−. The small dipole moment of the ${}^7{\Sigma }^{+}$ state is seen to be due to a large −MnH+ contribution from the nonbonding 8σ orbital (which is replaced by 4π in the ${}^7\Pi$ state). The manganese atom 3d⁵ configuration survives essentially unchanged in both states of MnH, and it is suggested that the electronic structure of other transition metal hydrides may be quite similar, involving a single ionic bonding σ orbital.