The luminescence spectra of CaWO4, CaMoO4, and ZnWO4 scintillating crystals were investigated in the temperature range 8–400K. The excitation photon energy was varied from the ultraviolet (4.5eV) to the hard x-ray region (35keV). It is found that as the excitation energy decreases the relative intensity of the low-energy luminescence band, attributed to the extrinsic emission of defect centers in CaWO4 and CaMoO4 crystals, increases. This observation is interpreted in terms of the total absorption of incident radiation, i.e., the variation of the mean penetration depth of the photons with their energy. It indicates that the centers responsible for the extrinsic emission in the crystals with scheelite structure are mainly localized in a thin (∼100nm) surface layer. On the other hand no noticeable changes with the excitation energy were found in the emission spectra of ZnWO4 crystals with wolframite structure. The possible implication of this finding is discussed. The light yield of the crystals is compared at low temperature using monochromatic x-ray excitation and it is shown that ZnWO4 has ∼10% higher light yield than CaWO4, while this parameter has a factor of 4 lower in CaMoO4.

No abstract

No abstract

No abstract

A new mobile end-station is described for use on multiple beamlines at the Daresbury synchrotron radiation source (overall excitation range 5 eV to 70 keV) that allows for the detection and dispersion of photoluminescence from solid-state samples in the emission range 190-1000 nm (1.2-6.5 eV). The system is fully self-contained and includes sample-cooling facilities for the temperature range 8-330 K using a closed-cycle refrigerator, thus eliminating the need for liquid cryogens. The system also includes solid-state laser sources for use with a variety of pump-probe-type experiments, and an Ar(+) surface-cleaning facility. In order to demonstrate the various capabilities of the system, the results of a variety of experiments are summarized, carried out over the excitation range 5-5000 eV on beamlines 3.2, MPW6.1 and 4.2. These include the optical detection of XAS of L-edge structure in natural minerals and archaeological ceramics, band-gap determinations of wide-band-gap silicates, and pump-probe studies of quartz.