EXCITATION MECHANISMS OF CSI FAST INTRINSIC LUMINESCENCE

For CsI single-crystal excitation spectra of fast intrinsic luminescen ce (FIL) peaking at 300 nm at 300 K, self-trapped exciton luminescence (280 and 340 nm) and impurity-induced emission (450 nm) have been mea sured in the VUV (20-130 eV) and X-ray (near L-3 edge of iodine) energ y regions. FIL excitation spectra were substantially different from th ose of other bands, FIL yield increases by a factor of more than 10 wi th the increase of the excitation energy from 20 to 50 eV, it also inc reases at L-3 edge of iodine, These regions are characterised by the i ncrease of local density of secondary electronic excitations. We sugge st that the relaxation of an exciton into FIL generating state occurs only in the region of the crystal perturbed by another electronic exci tation or defect.