[en] Two luminescence bands in the UV range were detected in crystalline α-quartz under electron beam excitation (6 kV, 3-5 μA). One band is situated at 5 eV and could be observed in pure samples. Its intensity increases with cooling below 100 K and undergoes saturation below 40 K alongside a slow growth with the time of irradiation at 9 K. The decay curve of the band at 5 eV contains two components, a fast (<10 ns) and a slow one in the range of 200 μs. The photoluminescence band at 5 eV with a similar temperature dependence was found in previously neutron-irradiated crystalline α-quartz. Therefore, the band at 5 eV was attributed to host material defects in both irradiation cases. The creation mechanism of such defects by electrons, the energy of which is lower than the threshold for a knock-out mechanism of defect creation, is discussed. Another band at 6 eV, containing subbands in different samples, appears in the samples containing aluminum, lithium and sodium ions. This luminescence is ascribed to a tunnel radiative transition in an association of (alkali atom)⁰-[AlO₄]⁺ that is formed after the trapping of an electron and a hole by Li⁺ (or Na⁺) and AlO₄

[en] A fast component of the self-trapped exciton (STE) luminescence was discovered in crystals with α-quartz structure such as SiO₂, SiO₂-Ge, GeO₂, AlPO₄ and GaPO₄, manifesting the singlet-singlet transitions of STEs. Comparison of time resolved photoluminescence (PL) spectra of triplet-singlet transitions and fast singlet-singlet transitions showed the singlet-triplet splitting of STEs in a pure SiO₂ α-quartz crystal to be 0.2 eV. In other crystals, the singlet-triplet splitting was found to be less than 0.2 eV. Small singlet-triplet intervals confirm that electrons of the STE are not confined in one atom's area

[en] Full text: The processes of excitation of the luminescence band at 4.75 eV in stishovite single crystal samples under x-ray and electron-beam irradiation were studied. Luminescence appears in a pure recombination process (thermally stimulated luminescence, long duration afterglow) under x-ray irradiation. A fast (about 10 ns, limited by resolution of measurement system) and a slow component of decay of luminescence, neither exponential nor pure hyperbolic, were detected under pulsed electron beam. The long duration x-ray excitation (tens of minutes) reveals a growth of the intensity. The character of the kinetics is dependent on the temperature, being fast at 290 K, it declines from the initial level at 200 K, and then for lower temperatures a rise-up appears. The result is explained as a luminescence center creation-destruction processes depending on temperature. This UV luminescence band could be observed even at 290 K, and, it was concluded that intra-center quenching of luminescence is not limiting the intensity. The thermal dependence of the intensity is determined mainly by peculiarities of the temperature dependence of the recombination process. The UV band of stishovite is compared with the cathodoluminescence band at 4.9 eV in α-quartz, which could not be created by x-ray irradiation. the latter is associated with transient centres created by destructive electron-beam irradiation or with permanent centres created by neutron or γ- irradiation, and with oxygen-deficient luminescence of silica glass

No abstract available

[en] Stishovite, coesite, oxygen deficient silica glass as well as irradiated α-quartz, exhibit two luminescence bands: a blue one and an UV one both excitable in the range within optical gap. There are similarities in spectral position and in luminescence decay kinetics among centers in these materials. The interpretation was done on the model of Oxygen Deficient Centers (ODC) [1]. The ODC(II) or twofold coordinated silicon and ODC(I) are distinguished. ODC(I) is object of controversial interpretation. The Si-Si oxygen vacancy [2] and complex defect including latent twofold coordinated silicon [3] are proposed. Remarkably, this luminescence center does not exist in as grown crystalline α-quartz. However, destructive irradiation of α-quartz crystals with fast neutrons, γ rays, or dense electron beams [4–6] creates ODC(I) like defect. In tetrahedron structured coesite the self trapped exciton (STE) luminescence observed with high energetic yield (∼30%) like in α-quartz crystals. STE in coesite coexists with oxygen deficient-like center. In octahedron structured stishovite STE was not found and only ODC exists

[en] Luminescence properties of SiO_2 in different structural states are compared. Similar comparison is made for GeO_2. Rutile and alpha-quartz structures as well as glassy state of these materials are considered. Main results are that for alpha-quartz crystals the luminescence of self-trapped exciton is the general phenomenon that is absent in the crystal with rutile structure. In rutile structured SiO_2 (stishovite) and GeO_2 (argutite) the main luminescence is due to a host material defect existing in as-received (as-grown) samples. The defect luminescence possesses specific two bands, one of which has a slow decay (for SiO_2 in the blue and for GeO_2, in green range) and an-other, a fast ultraviolet (UV) band (4.75 eV in SiO_2 and at 3 eV in GeO_2). In silica and germania glasses, the luminescence of self-trapped exciton coexists with defect luminescence. The latter also contains two bands: one in the visible range and another in the UV range. The defect luminescence of glasses was studied in details during last 60_70 years and is ascribed to oxygen deficient defects. Analogous defect luminescence in the corresponding pure nonirradiated crystals with ?-quartz structure is absent. Only irradiation of a alpha-quartz crystal by energetic electron beam, gamma-rays and neutrons provides defect luminescence analogous to glasses and crystals with rutile structure. Therefore, in glassy state the structure containing tetrahedron motifs is responsible for existence of self-trapped excitons and defects in octahedral motifs are responsible for oxygen deficient defects.

[en] Crystalline α-quartz doped with 0.1wt% and 0.9wt% germanium was studied using TSL and FGT equipment. Sample was chosen because previously it is known that Ge in quartz is efficient trap for electrons, therefore it could be used for detection of hypothetic self-trapped hole in α-quartz. However previous investigations of ODMR and TSL shows that in α-quartz the hole is still mobile and trapping occurs only on defect states. The activation energies for both TSL peaks are found by fractional glow and Hoogenstraaten method. The TSL distribution changes depending on Ge concentration and also on irradiation type. The TSL peaks below 70K in quartz doped with Ge could belong to hole trapped on Ge

[en] This work is devoted to the quantitative dosimetric support method for endoradyotherapy of inflammatory joints diseases. To reduce inflammation in synovium radiopharmaceutical is injected intraarticularly and provides local ablation of excessive synovial tissue. Present-day guidelines give empirical approaches to therapeutic activity selection. Such approaches lead to 20% untreated patients. Article shows way to improvement of cure level by introduction of dosimetric support. (paper)

[en] Full text: Luminescence and radiation damage under electron beam of germanium-doped crystalline α- quartz, pure silica glass with different deficiency of oxygen and thin film of silicon dioxide on silicon were studied. Luminescence and optical absorption spectra were measured at room temperature. The profile of the radiation damage was measured. The main effects are: 1. The transformation of the Ge center in crystal to the Ge related oxygen deficient center (GeODC) of glassy state was not found in spite of observation of an amorphous phase of the irradiated germanium doped α-quartz crystal. At small dose (0.1 C/cm²) an expansion of the irradiated volume was observed. At high dose (>1 C/cm²) a dilatation of the irradiated surface takes place. 2. In thin film of amorphous silicon dioxide on silicon the bulk NBO and the SiODC luminescence grows practically from a negligible initial level. 3. Pure silica samples with a different level of oxygen deficiency provide luminescence of SiODC centers under e-beam already at a low dose. Strongly deficient sample gives decrease of SiODC luminescence with dose, whereas more stoichiometric sample gives increase of luminescence with dose. The observed dilatation of the surface could be restored after heating to 1000 C. Therefore it is connected with densification of the irradiated volume. The CL spectrum of pure silica has additional red band of the NBO, when densification occurs. Therefore, beside densification of silica glass volume the three principal centers are recognized through absorption and luminescence in radiation processes under electron beam. These are: SiODC, NBO and E' center

No abstract available