Electron-phonon interaction in the V ²⁺:CsCaF ₃ laser crystal: Geometry of the [VF ₆] ^4- complex in the ⁴T _2g excited state

The dynamic T⊗e Jahn-Teller effect in the ⁴T _2g lowest excited state of the V ²⁺ ion in the CsCaF ₃ laser crystal is considered using an analysis of the ligands displacement due to the combined effect of the a _1g and e _g normal modes of the octahedral [VF ₆] ^4- complex. The net result of these vibrations is both axial and equatorial expansion by 0.02 and 0.12 , respectively. Electron-phonon coupling constants for the a _1g, e _g, t _2g normal modes were estimated using the experimental value of the crystal field strength Dq. The contour plot of the potential energy surface in the ⁴T _2g excited state was drawn; from that plot, the Jahn-Teller stabilization energy for the studied system was estimated to be 368.6 cm ^-1.