Subpicosecond deactivation of F center excitation by molecular defects in alkali halides

Abstract

An extremely rapid deactivation process of F center excitation has been observed in OH − or CN − doped alkali halide crystals. This superfast bleach recovery time of F center at 10.5 K is as short as ∼0.5 ps in CN − doped CsBr and ∼3 ps in OH − or OD − doped KCl and in OH − doped RbCl. The excitation of F H center is deactivated mainly by this superfast process which is due to energy transfer from the excited electronic F center into the stretching vibrational mode of the associated molecular defect via vibronic tunneling near the curve crossover point.