Time-resolved picosecond spectroscopy of the resonant secondary radiation of F centers in KCl

The linear polarization (P-HL) Of hot luminescence (HL) composing of the resonant secondary radiation of the F centers has been measured using a time-resolved picosecond spectroscopy over the whole Stokes wavenumber Omega range. The P-HL holds constant value of about 40% until the onset of ordinary luminescence (OL), from where it decreases to vanishingly small with decrease of Omega. This implies that the optically excited F center relaxes down along the 2p-like adiabatic potential energy surface (APES) trough, and transits to the 2s-like APES trough to form the relaxed excited state (RES). The lattice relaxation time and the dynamical transition rime are ultra fast estimated to be less than 15 psec.