Second2s−2plevel crossing at theFcenter in KCl evidenced by frequency upconversion spectroscopy

Abstract

Subpicosecond dynamics of resonant secondary emission from the F center in KCl at 5 K is investigated by frequency upconversion method. Detected photon energy range is from 0.65 to 1.55 eV and covers almost all the stationary emission band. The decay time of the luminescence intensity is longer in the low-energy side of emission band than in the high-energy side. A series of transient luminescence spectra shows relatively high intensities in the low-energy side. These two features indicate the existence of the second 2s-2p level crossing near the relaxed excited state.

Dynamics of nuclear wave packets at theFcenter in alkali halides

“…Theoretical consideration for the experimental results was given in [57]. Recently, we have investigated the dynamics of NWPs in the excited state at the F center in four alkali halides, KI [60,61], KBr [59], KCl [62,63] and RbCl [62] by time-resolved luminescence spectroscopy based on the frequency up-conversion technique. (See appendix B about the frequency up-conversion method.…”

“…Picosecond spectroscopy has been conducted for revealing the dynamics and has made considerable progress in understanding the 2s-2p state mixing [50][51][52][53][54]. Recent developments of ultrafast laser spectroscopy in the femtosecond regime have provided a renewed interest in the relaxation dynamics [55][56][57][58][59][60][61][62][63][64][65]. They have enabled us to perform real-time observations of lattice vibration as a motion of a nuclear wave packet (NWP) [56,57,59,[60][61][62][63]65].…”

“…Recent developments of ultrafast laser spectroscopy in the femtosecond regime have provided a renewed interest in the relaxation dynamics [55][56][57][58][59][60][61][62][63][64][65]. They have enabled us to perform real-time observations of lattice vibration as a motion of a nuclear wave packet (NWP) [56,57,59,[60][61][62][63]65].…”