Dichroism of absorption of $\mathrm{Cr}^{2+}$ centers in $\mathrm{KZnF}_3$ crystal under uniaxial stress

Observation of the intense linear dichroism spectrum on the $^5E_g\to^5T_{2g}$ transition of $\mathrm{Cr}^{2+}$ ions in $\mathrm{KZnF}_3$ crystal under uniaxial pressure is reported. The model is proposed, which assigns the observed spectrum to the alignment of the Jahn–Teller $\mathrm{Cr}^{2+}$ centers occurring as a result of the redistribution between the adiabatic potential minima of the $E\otimes e$ vibronic problem that become inequivalent under uniaxial pressure applied along the $C_4$ axis of the crystal. Analysis of the observed dependences of the dichroism signal amplitude on the applied pressure made it possible to estimate the electron-strain constant $V_{ES}=33600\pm1300$ cm$^{-1}$ and the tunnel splitting $\delta=12.9\pm1.6$ cm$^{-1}$, as well as to characterize the random strain field in the crystal.