Fine structure of the $^3$T$_1$($^3$H) $\to$ $^5$E($^5$D) transition in the Fe$^{2+}$ ion in iron-doped zinc selenide

Zero-phonon components of the Fe$^{2+}$ transition between inner shells of the Fe$^{2+}$ ion have been detected in low-temperature photoluminescence spectra of Fe-doped ZnSe crystals. Six spectral components corresponding to dipole-allowed transitions between the components $^3$T$_1$($^3$H) and $^5$E($^5$D) of the fine structure, which is caused by the spin–orbit coupling, have been reliably detected at temperatures of 5–10 K. The electronic spectrum of the Fe$^{2+}$ ion in the ZnSe matrix has been refined using the data obtained.