Optical and luminescence properties of CdWO4 and CdWO4:Mo single crystals

Abstract

-Luminescence properties of a pure CdWO 4 crystal and a CdWO 4 :Mo crystal doped with molybdenum in different concentrations have been investigated. The effect of molybdenum impurity on the intrinsic luminescence of CdWO 4 has been found, and the role of the impurity in the formation of new luminescence centers has been investigated. The features of the formation of the intrinsic and impurity luminescence excitation spectra of CdWO 4 and CdWO 4 :Mo crystals in the fundamental-absorption region have been considered. The reflection spectra of the CdWO 4 crystal have been investigated taking into account the crystal structure anisotropy. PACS numbers: 78.55.-m, 78.40.-q

Synchrotron and laser excitation of luminescence in PbWO4:Tb crystals at different temperatures

“…The observed intensity increase in the excitation spectrum of the intrinsic luminescence of PWO:Tb 3+ in the short-and long-wavelength regions when the temperature is lowered from 300 to 8 K may be caused by an increased probability of bonding to an exciton by isolated electrons and holes, since as the temperature is lowered the mean free path of the charge carriers through the crystals decreases and the effective radius of the recombination sphere increases [26]. The structure of the luminescence excitation spectrum of PbWO 4 :Tb 3+ at λ max = 420 nm and 8 K is generally similar to the excitation spectrum of this luminosity for PbWO 4 [3].…”

“…The excitation of the intrinsic luminescence at 300 K when PbWO 4 :Tb 3+ is irradiated by synchrotron radiation is weak because of the low probability that nonequilibrium, high-energy electrons and holes will thermalize with subsequent formation of an exciton [26]. The observed intensity increase in the excitation spectrum of the intrinsic luminescence of PWO:Tb 3+ in the short-and long-wavelength regions when the temperature is lowered from 300 to 8 K may be caused by an increased probability of bonding to an exciton by isolated electrons and holes, since as the temperature is lowered the mean free path of the charge carriers through the crystals decreases and the effective radius of the recombination sphere increases [26].…”

“…A sharp rise in the absorption in the region of the fundamental edge [4,29] leads to the appearance of a luminescence excitation maximum at 275 nm of excitons formed by a recombination mechanism. A further increase in the absorption coefficient causes a reduction in the depth to which the synchrotron radiation penetrates into the crystal and to an increase in the fraction of nonradiative decay of the electronic excitations near the surface [26,29], which causes the characteristic dip at high energies. The observed rise in the luminescence yield with excitation at d nm can be related to the photon multiplication effect [26,[29][30][31] and, possibly, to peculiarities in the band structure of lead tungstate.…”

The Luminescence of CdWO4:Tb,Li Crystals under Synchrotron Excitation at 10 K

“…It was shown in [9] that the doping of material by Li + ions leads to the increase of the transparency and the light yield of scintillator. The spectral characteristics of CdWO 4 luminescence at the excitation by synchrotron radiation are considered in [7,8,10]. It was shown in [8] that the luminescence spectrum of CdWO 4 at 10 K can be decomposed into two Gaussian components with maxima near 2.07 and 2.46 eV.…”

“…At room temperature CdWO 4 scintillators are characterized by a low afterglow, a high yield of luminescence with maximum in 2.482.50 eV region and a decay time ≈ 10 µs [24,7,8].…”