Intrinsic radioluminescence of non-ionizing electrons and Auger-free holes in dielectrics excited by high-current-density electron beams

Two kinds of intrinsic luminescence in dielectrics being excited by high-current-density electron beam are investigated using experimental and theoretical methods. The first one is the intraband radioluminescence (IBRL) generated by direct radiative transitions of non-ionizing electrons within the conduction band. The second one is the band-to-band (interband) radioluminescence (BBRL) generated by radiative transitions of Auger-free holes from the lower valence band to the upper. IBRL was discovered and studied by authors in 1972-80. It may be induced by electron, ion, X-ray or even laser beam if the latter generates secondary electrons of 1-20 eV above the conduction band bottom. If the pulse of irradiation is short (0.1-10 ps) or temperature of the sample is high (more than 600 K) then the IBRL is the brightest component of dielectric light emission. IBRL is shown to have some extreme properties in comparison with all other forms of luminescence: the broadest continuous spectrum (1-25 eV), the shortest lifetime (0.1-1.0 ps) the ´absolute´ independence on temperature up to boiling point. The BBRL is generated if Auger-free range of dielectric electron spectrum includes two valence bands or more. It was discovered in 1984. The both kinds of intrinsic radioluminescence-IBRL and BBRL-have been observed simultaneously in CsI crystals using pulsed power electron beam for excitation. The theoretical model of observed light emission as the superposition of IBRL of conduction non-ionizing electrons and BBRL of valence Auger-free holes is in quantitative accordance with the main experimental data including detailed spectra, quantum yield of 10/sup -4/-10/sup -3/, very weak dependence on temperature and static disorder, subpicosecond lifetime etc. Applications of IBRL and BBRL for pulsed power beams diagnostics and dielectric physics are discussed.