It was recalled that, in many alkali halides, the aggregation of CN- to F-centers created an environment for energy transfer. In crystals such as CsCl, very efficient energy transfer occurred from the excited F-center to the CN- N = 4 and 5 vibrational states. A model was developed, for this energy transfer, which offered some insight into the F-center crystal environment. By changing the environment which was experienced by the CN- very quickly, a reasonable potential could cause a transition to the CN- N=5 vibrational state. It was noted that the lattice and CN- transitions were connected by energy conservation.

S.Pilzer, W.B.Fowler: Materials Science Forum, 1997, 239-241, 473-6