Crystal field analysis, electron-phonon coupling and spectral band shape modeling in MgO:Cr³⁺

A crystal field analysis of the energy level structure of Cr³⁺ in MgO crystal is performed, using the exchange charge model of the crystal field theory. The crystal field parameters acting on the optical electrons of Cr³⁺ are calculated from the crystal structure data; good agreement between the calculated and observed energy levels of Cr³⁺ in the title host is demonstrated. The Stokes shift S = 5.9 and the energy of the phonons effectively interacting with the impurity center hℏω = 405 cm^-1 are derived from the experimental spectra of absorption and emission. The obtained values of S and hℏω were used for the computer modeling of the Cr^{3+ 4}T_2g → ⁴A_2g emission and ⁴A_2g → ⁴T_2g absorption bands. From this modeling, the zero-phonon energy for the considered transitions was estimated to be 14,000 cm ^-1.