Formation Time of STE at 1Σ+u State in RbBr and KI under Pulsed Electron Beam in Picosecond Range

The growth times (τ g σ ) of the σ emission intensity in RbBr and KI crystals have been obtained to be 10±10 ps and 5±5 ps, respectively, under irradiation of a pulsed electron beam with the pulse duration of about 18 ps near liquid helium temperature. τ g σ includes both the life time of the conduction electron and the relaxation time of electrons from the conduction band down to the 1 Σ + u (σ u , 2 s σ g ) state of the self trapped exciton. τ g σ is discussed in connection with the formation mechanism of the F - H center pair. The decay times (τ d σ ) of the emission intensity in these crystals are 3.3±0.1 ns and 1.6±0.1 ns, respectively, in good agreement with those observed by using a pulsed proton beam with nsec pulse duration by Blair et al .