Thermochemistry of the Molecular Species LiO, LiO+, and Li2O+

Abstract

Molecular species in the $\mathrm{Li–O}$ system were studied by electron‐impact mass spectrometry and the data were used to derive the dissociation energy of LiO and the ionization potentials of LiO and Li₂O. From studies of the gaseous equilibria Li+O₂=LiO+O and Li₂O+O=2LiO and from the composition of saturated vapor over Li₂O(c), the value $D_0^0(\mathrm{LiO}\text{)=80.5 ± 1.5\hspace{0.17em}}\mathrm{kcal}\text{\hspace{0.17em}(3.49 ± 0.06\hspace{0.17em}}\mathrm{eV})$ is obtained. The ionization potentials were found to be I.P.(LiO) =8.45 eV and $\mathrm{I.P.}({\mathrm{Li}}_2\mathrm{O}\text{)=6.19\hspace{0.17em}}\mathrm{eV}$ with an uncertainty of 0.20 eV, leading to ${\mathrm{\Delta \; Hf}}_0^{\mathrm{o}}({\mathrm{LiO}}^{+}\text{)=211.5\hspace{0.17em}}\mathrm{kcal/mole}\text{\hspace{0.17em}(9.17\hspace{0.17em}}\mathrm{eV})$ and ${\mathrm{\Delta \; Hf}}_0^{\mathrm{o}}({\mathrm{Li}}_2{\mathrm{O}}^{+}\text{)=103.1\hspace{0.17em}}\mathrm{kcal/mole}\text{\hspace{0.17em}(4.47\hspace{0.17em}}\mathrm{eV}\mathrm{).}$ The data are compared with the results of some theoretical calculations, and the chemical bonding in these molecules is discussed briefly.