Electron Spin Resonance and Optical Spectra ofV2+in NaCl

The ESR and optical spectra of ${\mathrm{V}}^{2+}$ in NaCl show that there are two species of ${\mathrm{V}}^{2+}$, one of which is situated in a tetragonal and another in an orthorhombic site. Optically, three weak bands corresponding to transitions between Stark levels and one strong electron-transfer band were detected which yield the crystal field strength $\Delta =8190\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$ and the Racah parameter $B=559\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. Two long-wavelength bands show some structure which is probably due to splitting by low-symmetry fields. The $g$ shift and zero-field splitting of the center in the tetragonal site suggest that the $d$ orbitals are considerably distorted by covalency.