Analysis of optical spectra of v²⁺ centres in ZnS and ZnSe single crystals

A systematic spectroscopic study of V²⁺ -doped ZnS and ZnSe single crystals (which includes crystal growth, absorption spectra measurements and combined application of the crystal field calculations and first-principles analysis of V²⁺ energy levels and absorption spectra) is reported. Detailed comparison between the calculated energy levels and experimental absorption spectra enabled the assignment of the absorption peaks. The dependence of the crystal field and covalent effects on the interionic distance is analysed qualitatively. Several existing discrepancies between various literature data concerning the order of the V²⁺ energy levels (in particular, the positions of the ²E and ⁴T₁ (⁴P) levels) are resolved.