Up to 30 times enhancement of deep UV emission at room temperature by prolonged excitation of localized exciton in NaCl:I crystal

A material emitting DUV light at room temperature is promising for an application to a new laser action. We report the remarkable phenomena that deep ultra-violet (DUV) emission at 220 nm, so-called NE emission, in NaCl:I crystal is enhanced up to 30 times at room temperature by prolonged excitation of the localized exciton. Such an accumulated effect is kept even if the excitation is interuped for a few minutes but is completely reset by white light irradiation at room temperature. The phenomena are discussed considering thermal ionization of iodine anion by the VUV light excitation, trapping of dissociated electrons in hole centers and recombination of electrons and iodine hole centers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)