The KrCl excimer laser irradiation (5.58eV) of monocrystals at about 150K was found to produce F, F’, ,  and V centers. The V centers gave rise to V2 and V3 bands which exhibited <100>-type dichroism. In crystals which contained V centers, the 111/cm Raman line which originated in the symmetrical stretching vibration mode of an I3- molecular ion appeared. On the basis of the I3- molecular ion model for the V center, the V2 and V3 bands were attributed to relatively stronger transitions from the ground state to various excited states. The splitting of these 2 bands was attributed mainly to spin-orbit interactions.

T.Okada: Molecular Physics, 1995, 86[5], 1075-84