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The role of fluorine doping on silica has been studied through comparison of the luminescence of fluorine doped and fluorine-free samples made by melting in on SiF4 atmosphere and excited by an ArF laser (6.4 eV) in the temperature range 10–290 K. The fluorine doped sample possesses a very weak absorption band at 7.6 eV on the level of 0.1 cm−1 and there the photoluminescence of so-called oxygen-deficient centers in the blue (2.7 eV) and UV bands (4.4 eV) could be excited. The same luminescence bands are observable in the fluorine-free sample, which contains an absorption band at 7.6 eV on the level of 20 cm−1. In the fluorine-doped sample the UV band prevails over the blue band. This effect can be explained as the influence of fluorine in quenching intra-center transitions probabilities and the fast UV luminescence being less affected than the longer-lived blue luminescence. The photoluminescence spectra, their decay kinetics and temperature dependence were measured under ArF laser irradiation (6.4 eV). The main effect is the observation of decay components for the UV band in the microsecond time scale, which is slower than the usual decay which is normally measured in the ns time scale. The blue band also possesses a decay in the microsecond range, which is much faster than the ‘normal’ decay of this band in the millisecond range. The decay becomes faster, however the intensity increases with increasing temperature indicating the participation of atomic (ionic) mobile particles in the recombination processes. The details of the kinetics are slightly different in fluorine-doped and fluorine-free samples. The observed effects can be explained in terms of the recombination process of defects created under ArF laser excitation. [Copyright &y& Elsevier]

Abstract: We report on observation of upconverted VUV luminescence due to 5d–4f radiative transitions in Er3+ and Nd3+ ions doped into some fluoride crystals, under excitation by ArF and KrF excimer lasers, respectively. Only spin-forbidden 5d–4f luminescence of Er3+ (at 165nm) was detected from the LiYF4:Er3+ crystal whereas both spin-forbidden (at 169nm) and spin-allowed (at 160.5nm) components are observed from the BaY2F8:Er3+ crystal, the latter being much weaker than in the case of one-photon excitation. Nd3+ 5d–4f luminescence at 180 and 173nm has been detected from the LiYF4:Nd3+ and LaF3:Nd3+ crystals, respectively. The shift of short-wavelength edge of 5d–4f emission spectra towards longer wavelengths is observed under temperature increase from 15 to 293K. The observed effects in the spectra of Er3+ and Nd3+ doped crystals were interpreted as a result of reabsorption of 5d–4f luminescence escaping from the bulk of the crystals. [Copyright &y& Elsevier]