Temperature‐Dependent Ground State Splitting of Mn⁺⁺ Ions in Alkali Halides Induced by Resonant Vibrations

The temperature dependence of the rhombic ground state splitting tensor D of Mn ++ centres with nearest cation vacancy was measured at NaCl and LiCl. The experimental data reveal a behaviour of the tensor D , which can be described by D ( T ) = D 0 + D coth ℏ ω/2 kT. This result is interpreted by assuming a resonant vibration of frequency w coupling to the centre. This vibration changes the rhombic crystalline fields which produce the ground state splitting of the Mn ++ ion according to the theory of van Heuvelen [4]. It is possible to find resonant modes in both systems NaCl and LiCl which lead to good agreement between the calculated and the experimental data.