Abstract
For part I see Phys. Rev. B, vol.4, 2757 (1973). The model takes the origin of the far-infrared lines as transitions corresponding to the quantized translational motion of the impurity in the matrix cage, and then considers the effect of various perturbing mechanisms on it. It is found that the theory can explain the multiplet structure for the KCl-6Li+ and KCl-7Li+ systems in terms of a (111) displacement direction of the impurity ion. The unexplained results are discussed in terms of the recent trend of work in this field, and the results are compared with those of other existing models. For the NaCl-Li+ system also, an attempt has been made to explain the observed doublet structures and their relative intensities in terms of the present theory. However, a correct explanation could not be achieved. This indicates that this system is probably not an example of an off-centred impurity.