Energy-level assignments for the1Eand3T1astates of MgO:Ni2+

The ${}_{}{}^1{}_{}{}^{}$ ${\mathit{T}}_2$ ${\to }^1$E${,}^3$ ${\mathit{T}}_1$a luminescence, and the ${}_{}{}^3{}_{}{}^{}$ ${\mathit{T}}_2$ ${\to }^1$E${,}^3$ ${\mathit{T}}_1$a excited-state absorption spectra of MgO:${\mathrm{Ni}}^{2+}$ have been observed for the first time. These data are used in conjunction with the conventional ground-state absorption spectrum, to determine the energy-level assignments for the ${}_{}{}^3{}_{}{}^{}$ ${\mathit{T}}_1$a and ${}_{}{}^1{}_{}{}^{}$E states. In particular, three of the four spin-orbit components of the ${}_{}{}^3{}_{}{}^{}$ ${\mathit{T}}_1$a state are identified. Although the ${\mathit{A}}_1$ spin-orbit component is broadened beyond recognition, the ${\mathit{T}}_1$ component is directly observed as a magnetic-dipole allowed transition in the ${}_{}{}^3{}_{}{}^{}$ ${\mathit{T}}_2$ ${\to }^3$ ${\mathit{T}}_1$a excited-state absorption spectrum. Lastly, the energies of the ${\mathit{T}}_2$ and E spin-orbit levels are inferred from the positions of their vibrational sidebands in the ground-state absorption spectrum.