Knowledge Bank

Weak d electron transitions of $V2+$ and $Cr3+$ ions in doped MgO may be obscured by far more intense charge-transfer bands such as those due to $Fe3+$. Both the $V2+$ and $Cr3+$ display a sharp-line fluorescence ($\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}E⟶4A2$), very similar to that of the R-lines in ruby. Hence one may demonstrate existence of weak absorption bands by measuring the excitation spectrum of this fluorescence. The higher energy $\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}A2⟶4T1$ which has not heretofore been observed for $V2+$ and $Cr3+$ has been established in this way. A band reported by $Low1$ is not observed.