Thermalized and Hot Interstitial Halogen Ions in Alkali Halides

The efficiency of α, I pair creation at exciton decay is high at 4.2 K for KCl, KBr, and RbBr crystals for which H centers are oriented along 〈110〉. The efficiency of α, I pair creation by VUV-irradiation at 4.2 K is extremely low for NaCl crystals for which H centers are oriented along 〈111〉. The process of mobile crowdion-type interstitial halogen ion (I center) formation in KCl, KBr, RbCl, and RbBr (but not in NaCl) due to the tunneling recharge of primary F, H pairs is discussed. Such an I crowdion can shift by several interanion distances along [110] even at 4.2 K and, as a result, the system leaves the zone of spontaneous annihilation of α and I centers.