Vibronic coupling effect on Fe2+ Mossbauer quadrupole splitting in CsCoCl3

The effect of vibronic coupling (orbit-lattice interaction), which produces a mixing between the low-lying electronic states with the emission and abs orption of phonons of varying energies, is considered to explain the observ ed temperature dependence of Mossbauer quadrupole splitting of Fe2+ ions in CsCoCl3 over 22 to 300 K. The various lattice dynamical parameters are est imated and then quadrupole splitting is explicitly calculated as a function of temperature. One obtains a reasonably good agreement with the experimen tal data, which shows that the vibrating lattice model is quite realistic a nd important.