Cr²⁺ excitation levels in ZnSe and ZnS

Abstract

The excitation spectrum of the IR emission 5 A 1 ( 5 E) to 5 B 2 ( 5 T 2 ) of substitutional Cr 2+ in ZnSe displays, as in the case of ZnS, band-band transitions, photoionization of activator centres, and a structured region of inner transitions towards higher levels of the Cr 2+ ions. In the crystal-field approximation, a fitting of the eigenvalues of the Tanabe-Sugano matrices to the excitation bands supplies the crystal-field parameter Dq and the Racah parameters B and C. This fitting and the fact that both for ZnSe and for ZnS, one specific excitation band depends on pre-treatment, suggest a slightly modified interpretation of the ZnS excitation spectra.