Papers by Liudmila Lisitsyna
Soviet physics. Solid state, 1990
Spectral-kinetic characteristics of photo-and katodoluminescens were observed in the spectral ran... more Spectral-kinetic characteristics of photo-and katodoluminescens were observed in the spectral range 3.7-1.6 eV of LiF crystals activated by oxygen: LiF-O, LiF-OH and -LiF-WO3 . We used pulsed spectrometry with nanosecond time resolution in the temperature range 15-300 K and the range of absorbed doses 1.6·101 -103 Gy. The temperature dependence of the efficiency of radiation to create molecular ions O2 - and the characteristic decay time of the long-lived and short-lived component of the pulsed cathodoluminescence in crystals LiF-OH, LiF-WO3 is investigated. For the study the optical absorption spectra in the spectral range of 1-6 eV and the transmission spectra of 0.1-0.5 eV is not irradiated and irradiated with electrons LiF-O, LiF-OH, LiF-WO3 crystals used Spectrophotometer SPh-256 and IR- Fourier spectrometer Nicolet 5700. Comparative analysis of the studied materials makes it possible to determine the influence of type of oxygen impurity in the lattice and related defects (poly...
Soviet physics. Solid state, 1992
The relaxation kinetics of F 2 + centers were investigated in a crystal of LiF containing previou... more The relaxation kinetics of F 2 + centers were investigated in a crystal of LiF containing previously formed color centers and then exposed to a radiation pulse. A study was made of the dependence of the relaxation kinetics and its various stages on the temperature of a sample during irradiation, as well as on the energy density of a radiation pulse and the initial number of defects. Quantitative relationships were established between these factors and the parameters of the relaxation kinetics. A mathematical model was developed for the description of the kinetics of relaxation of F 2 + centers after the action of a radiation pulse
Bulletin of the Russian Academy of Sciences: Physics, 2020
The paper presents the results of YAG:Ce phosphors luminescence under excitation in 4.0-6.2 eV ex... more The paper presents the results of YAG:Ce phosphors luminescence under excitation in 4.0-6.2 eV excitation region by excilamp radiation. It is shown that excitation in the UV region leads to the appearance of bands at 320 and 370 nm. The ratio of the bands at 320, 370, and 560 nm depends on the excitation wavelength. It is assumed that the excitation energy is absorbed by nanodefects and transferred to the luminescence centers being in their composition.
Journal of Physics: Conference Series, 2017
IOP Conference Series: Materials Science and Engineering, 2016
The results of studies of emission properties of oxygen-containing ZnWO4 crystals are presented. ... more The results of studies of emission properties of oxygen-containing ZnWO4 crystals are presented. Oxygen is incorporated into single crystals in two ways: annealing of crystals at 900 C in an oxygen atmosphere and implantation of high energy (28 MeV) oxygen ions. The observed variation of the photoluminescence intensity and excitation spectrum of emission at 2.6 eV are interpreted as the occurrence of a concentration gradient of emission centers in the crystal bulk under hearting of crystals and the dependence of the photons mean penetration depth in a crystal on their energy. In order to gain better insight into the nature of the phenomenon, time-resolved luminescence measurements were carried out.
The paper presents the results of the research of the F 2 centers accumulation dose dependences i... more The paper presents the results of the research of the F 2 centers accumulation dose dependences in the LiF crystals, the kinetics of absorption relaxation initiated by exposure to a single electron pulse in the band maxima of different electron centers obtained by time-resolved spectrometry with nanosecond resolution. An analytical description of the F 2 center accumulation in an absorbed dose range ≤10 3 Gy is provided.
Russian Physics Journal, 2015
Results of investigations into the scintillation properties of ZnWO 4 crystals with different pre... more Results of investigations into the scintillation properties of ZnWO 4 crystals with different prehistory are presented. A model of the processes leading to a dependence of the luminescence intensity on the depth of penetration of exciting radiation into the material is suggested.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2015
The paper presents the investigation results on the effect of the oxygen incorporation modes on s... more The paper presents the investigation results on the effect of the oxygen incorporation modes on spectroscopic properties of ZnWO 4 crystals. Oxygen is incorporated into single crystals in two ways: in annealing at 900°C in oxygen atmosphere and implantation of high energy (28 MeV) oxygen ions. It was found that the changes in the state of the crystal surface under different treatments lead to interesting differences in the emitting properties of the material. In order to gain better insight into the nature of the phenomenon, time-resolved luminescence measurements were carried out.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2016
Non-radiative decay of the electronic excitations (excitons) into point defects (F-H pairs of Fre... more Non-radiative decay of the electronic excitations (excitons) into point defects (F-H pairs of Frenkel defects) is main radiation damage mechanism in many ionic (halide) solids. Typical time scale of the relaxation of the electronic excitation into a primary, short-lived defect pair is about 1-50 ps with the quantum yield up to 0.2-0.8. However, only a small fraction of these primary defects are spatially separated and survive after transformation into stable, long-lived defects. The survival probability (or stable defect accumulation efficiency) can differ by orders of magnitude, dependent on the material type; e.g. $10% in alkali halides with f.c.c. or b.c.c. structure, 0.1% in rutile MgF 2 and <0.001% in fluorides MeF 2 (Me: Ca, Sr, Ba). The key factor determining accumulation of stable radiation defects is stabilization of primary defects, first of all, highly mobile hole H centers, through their transformation into more complex immobile defects. In this talk, we present the results of theoretical calculations of the migration energies of the F and H centers in poorely studied MgF 2 crystals with a focus on the H center stabilization in the form of the interstitial F 2 molecules which is supported by presented experimental data.
IOP Conference Series: Materials Science and Engineering, 2015
The spectral and kinetic characteristics of the emission of Sn-and Fe-doped Ga 2 O 3 crystals exc... more The spectral and kinetic characteristics of the emission of Sn-and Fe-doped Ga 2 O 3 crystals excited by a nanosecond electron beam are studied. A new cathodoluminescence band of the Fe-doped crystal is revealed with a maximum at λ m = 315 nm. Comparison with the data obtained with a subnanosecond duration of the beam current pulse is performed. It is shown that, with increasing duration of the beam current pulse, the main contribution is made by cathodoluminescence in the range of 300-450 nm.
Soviet Physics Journal, 1972
Russian Physics Journal, 1992
The pulsed absorption and luminescence spectrometry techniques with time resolution are used to s... more The pulsed absorption and luminescence spectrometry techniques with time resolution are used to study the processes of creation and postradiative destruction of F2−-centers in the time interval 10−8-105 sec following exposure of LiF crystals with different sets of preliminarily introduced color centers to a radiation pulse in the temperature interval 80–400 K. The accumulated data on kinetics of the relaxation of F2−+, F2−, and F2−− absorption and radioluminescence bands of the crystal are used to provide a phenomenological description of the charge evolution of an F2-center leading to the formation of F2−+ and F2−− centers due to thermally activated variation of the spin of an F2-center under the action of radiation. A mathematical description is provided for the kinetics of relaxation of absorption of F2−-centers initiated by a radiation pulse, and the energy and kinetic parameters are determined for the processes of formation and destruction of F2−-centers.
Journal of Applied Spectroscopy, 1990
Russian Physics Journal, 1996
Pulsed-spectrometric research shows that the presence of defects, including those that are electr... more Pulsed-spectrometric research shows that the presence of defects, including those that are electrically neutral with respect to the crystal lattice, has a significant influence on the distribution of the radiation-induced electron excitations. This is evident in the electron-excitation sink in the vicinity of defects and the formation of localized excitons around impurities in ionic crystals. This influence of defects on the electron-excitation distribution is probably due to deformation of the lattice in the region of the defect. It is shown that, in the region of the defect, there is oscillating potential relief, the presence of which leads to the capture of charge carriers and their localization in this region. Lattice distortion because of deformation in the region of the defect changes the mutual distribution of the ion pairs. This creates conditions for the effective conversion of electronic excitations to localized near-defect dihalide excitons, which are different from those created in an ideal lattice.
Soviet Physics Journal, 1969
A study of two types of additional absorption spectra observed in colored CaF 2 crystals is repor... more A study of two types of additional absorption spectra observed in colored CaF 2 crystals is reported. The spectral shape for the additively colored crystal is governed by the experimental conditions; during photochemical coloring, it depends on the thermal prehistory of the sample. In all cases, a spectrum consisting of bands at 370 and 560 nm appears in crystals having a band near 200 nm. An additional band appears at 560 nm in the Smakula spectrum at high-irradiation doses; there are three stages in the increase of this band with increasing dose. A similar dependence on the radiation dose is observed for the 560-nmband in synthesized CaF 2 crystals. It is suggested that this band is due to defects produced in the lattice during the irradiation.
Inorganic Materials, 2008
The promising phosphor LiF〈U〉-O has been studied by nanosecond-resolution pulsed spectrometry. Th... more The promising phosphor LiF〈U〉-O has been studied by nanosecond-resolution pulsed spectrometry. The uranium and oxygen luminescence buildup and decay characteristics have been measured at 300 K. The uranium luminescence buildup under nanosecond electron excitation has been shown to involve two steps. The effect of pulsed electron irradiation on the activator luminescence efficiency has been assessed.
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Papers by Liudmila Lisitsyna