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1.
The energy level structure of F
3
+
laser color centers in crystals of LiF is discussed. A high-power laser (λ
ex=920 nm) is used to excite luminescence from LiF crystals with F
3
+
centers via two-photon absorption, and the dependence of the polarization and intensity of this luminescence on the polarization
of the laser light is measured and calculated. It is shown that the two-photon transition involves the excitation of a previously
unknown state of the F
3
+
center—a spin singlet whose wave function has 1
A
1 symmetry.
Fiz. Tverd. Tela (St. Petersburg) 39, 1373–1379 (August 1996) 相似文献
2.
T. Tsuboi 《Applied physics. B, Lasers and optics》1999,69(1):81-83
A stable, free-running LiF:F3
− and LiF:F2
− color center laser oscillation is achieved at room temperature by pumping with the 930-nm laser radiation. The LiF:F3
− laser radiation has a peak at 1100 nm and shifts from the peak wavelength of the F3
− luminescence band because of the absorption of the F3
− luminescence by the F2
− center, which co-exists with the F3
− center.
Received: 2 March 1999 / Revised version: 16 March 1999 / Published online: 12 May 1999 相似文献
3.
L. A. Lisitsyna 《Russian Physics Journal》1996,39(11):1050-1066
The processes of creating and transforming electronic color centers in an LiF crystal irradiated with a nanosecond electron
pulse are investigated using pulse spectrometry with nanosecond resolution for times in the range 10−8 to 105 sec. It is shown that the thermally activated mechanism of forming Frenkel pairs in the 12–200 K range consists of successively
creating exciton states, as the temperature rises, having different degrees of spatial separation of the electron and hole
components. It is concluded that the structure of self-trapped excitons evolves as a function of temperature and time, and
that this evolution commences for any alkali halide crystal with the creation of self-trapped excitons ofD
2h point symmetry at 4 K. It is established that the interaction of electronic excitations with electronic color centers changes
the properties of both the electronic excitations themselves and the color centers. In a crystal containing neutral electronic
centers there is a fall in the yield of self-trapped excitons and Frenkel pairs and an increase in the contribution of the
radiative channel for loss of the irradiation energy by the color centers. A mechanism is proposed for exciting luminescence
of electronic color centers. It is established that short-lived irradiation-induced states exist, in particular a change in
the spin state or in just the energy state of a center in the irradiation field, and that the appearance of these states changes
the efficiency and directivity of the charge evolution of the electronic color centers.
State Architectural Building Academy, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 57–75,
November, 1996. 相似文献
4.
Five types of passive Q-switched as well as simultaneously Q-switch mode-locked modulators: plastic dye sheets (Kodak 9850
cellulose acetate dye sheets), lithium fluoride crystals containing F2
− color centers (LiF:F2
−), chromium-doped yttrium–aluminum–garnet crystals (Cr4+:YAG), ionic color filter glass (Schott RG1000 color filter glass), and the single crystal semiconductor wafers (GaAs, Fe-doped
InP, Zn-doped InP, S-doped InP, etc.) used for modulation of the Nd:hosted(Nd:YAG, Nd:YVO4, and Nd:LSB) lasers were investigated in detail in our research. We also investigated applications of the Q-switch mode-locked
pulse train for the development of a higher resolution solid-state laser range finder. 相似文献
5.
S. S. Novosad 《Technical Physics》1999,44(1):124-125
The effect of the conditions of preparation, temperature, and the action of x rays on the luminescence properties of calcium-iodide
scintillation crystals is investigated. On the basis of the results of a study of the spectral characteristics of CaI2 and CaI2:H2 crystals for optical and x-ray excitation in the temperature range 90–400 K, also taking into account the results of a study
of the luminescence properties of CaI2 crystals activated by Cl−, Br−, OH−, and Ca2+ impurities, it is suggested that the 236-nm band observed in the excitation spectra of crystals of calcium iodide may be
caused by an uncontrollable hydrogen impurity. The luminescence of these crystals with maximum at 395 nm is ascribed to radiative
recombination of excitons trapped at H− ions.
Zh. Tekh. Fiz. 69, 135–136 (January 1999) 相似文献
6.
Yu. L. Gusev S. I. Marennikov V. P. Chebotayev 《Applied physics. B, Lasers and optics》1977,14(1):121-122
Frequency-tunable generation by means of F
2
+
and F
2
−
colour centers in a LiF crystal is reported. Colour centers were created by illuminating LiF crystals with electrons of 3
meV energy at the electron current density of 1 μA/cm2. The pumping source was a ruby laser with a peak power of 20 MW, a pulse duration of 20 ns, and a repetition rate of 1 Hz.
The frequency tuning is obtained in the range of 0.88–1.25 μm. Discussed are the ways of pumping of colour centers and the
possibility of lasing in the spectral region of 0.85 to 2 μm in the type of colour centers under investigation. 相似文献
7.
Data presented on the influence of the temperature in the range 80–650 K on the spectral kinetics of the luminescence and
transient absorption of unactivated CsI crystals under irradiation by pulsed electron beams (〈E〉=0.25 MeV, t
1/2=15 ns, j=20 A/cm2). The structure of the short-wavelength part of the transient absorption spectra at T=80–350 K exhibits features, suggesting that the nuclear subsystem of self-trapped excitons (STE’s) transforms repeatedly
during their lifetime until their radiative annihilation at T⩾80 K, alternately occupying di-and trihalide ionic configurations. It is established that a temperature-induced increase
in the yield of radiation defects, as well as F and H color centers, and quenching of the UV luminescence in CsI occur in the same temperature region (above 350 K) and are characterized
by identical thermal activation energies (∼0.22 eV). It is postulated that the STE’s in a CsI crystal can have a trihalide
ionic core with either an on-center or off-center configuration; the high-temperature luminescence of CsI crystals is associated
with the radiative annihilation of an off-center STE with the structure (I−(I0I−
e
−))*.
Fiz. Tverd. Tela (St. Petersburg) 40, 640–644 (April 1998) 相似文献
8.
I. N. Ogorodnikov A. V. Porotnikov A. V. Kruzhalov V. Yu. Yakovlev 《Physics of the Solid State》1998,40(11):1817-1822
A study of recombination kinetics in LiB3O5 (LBO) crystals by time-resolved luminescence and absorption spectroscopy is reported. An investigation of the kinetics of
transient optical absorption (TOA) and luminescence under ns-scale electron-beam excitation performed within a broad temperature
range of 77–500 K and a 1.2–5-eV spectral interval has established that the specific features in the recombination kinetics
observed in LBO involve electronic, B2+, and hole, O−, trapping centers. The TOA and luminescence kinetics, as well as their temperature dependence, are interpreted by a model
of competing hole centers. Relations connecting the kinetics parameters and the temperature dependence to the parameters of
the main LBO point defects are presented.
Fiz. Tverd. Tela (St. Petersburg) 40, 2008–2014 (November 1998) 相似文献
9.
We investigate the spectra of the x-ray radiation-induced absorption of SrCl2−Ce crystals over the spectral range 345–830 nm and their temperature transformations in the interval from 77 to 450 K. We
found that radiative color centers are characterized by a complex spectrum of induced absorption that contains wide bands
of photochromic PC (750, 519, 378 nm) and PC+ (620, 446, 340 nm) centers and quasi-linear bands of Ce2+ centers. The most significant thermal transformations of radiative color centers occur in the vicinity of the thermostimulated
luminescence peak of 394 K, at which the holes of the PC+ centers recombine with the electrons of the Ce2+ centers.
Ivan Franko L’vov State University, 8, Kirilla i Mefodiya St., L’vov 290005, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 64, No. 4, pp. 545–547, July–August, 1997. 相似文献
10.
L. C. Courrol R. E. Samad L. Gomes I. M. Ranieri S. L. Baldochi A. Z. Freitas S. P. Morato N. D. Vieira Jr. 《Laser Physics》2006,16(2):331-335
Color centers are lattice vacancy defects trapping electrons or holes. They are easily created in single crystals by irradiation with ionizing radiation. We report the production of color centers in LiF and LiYF4 single crystals by ultrashort high-intensity laser pulses (60 fs, 12.5 GW). An intensity threshold for color center creation of 1.9 and 2 TW/cm2 was determined in YLF and LiF, respectively, which is slightly smaller than the continuum generation threshold. Due to the high energy density of the coherent radiation of the focused laser beam, we were able to identify a large amount of F centers, which gave rise to aggregates such as F2, F 2 + , and F 3 + . The proposed mechanism of formation is based on multiphoton excitation, which also produces short-lived F 2 + centers. It is also shown that it is possible to write tracks in the LiF crystals with dimensional control. 相似文献
11.
The effect of weak magnetic fields (0.1–0.8 T) on the internal friction and Young’s-modulus defect of LiF crystals is investigated
over a range of relative strain amplitudes ɛ
0 from 10−6 to 10−4 at frequencies of 40 and 80 kHz. Experiments with these fields show that the internal friction increases and the effective
elastic modulus decreases, indicating an increase in the plasticity of the samples. Plots are obtained of the internal friction
versus the magnitude of the magnetic field at various values of the strain amplitude ɛ
0.
Fiz. Tverd. Tela (St. Petersburg) 41, 1035–1040 (June 1999) 相似文献
12.
Yu. V. Zorenko R. M. Turchak T. I. Voznyak A. P. Luchechko 《Journal of Applied Spectroscopy》2006,73(2):211-215
By liquid-phase epitaxy from an aqueous alcoholic solution, we have obtained films of the well-known storage phospor CsBr:Eu,
and we have studied their cathodoluminescence and photoluminescence (PL) spectra compared with the undoped CsBr films. We
have established that the structure of the photoluminescence centers of the CsBr:Eu films when excited by laser radiation
in the absorption band of the Eu2+ ions (λ = 337 nm) includes Eu2+-VCs isolated dipole centers and CsEuBr3 aggregate centers, and also luminescence centers based on inclusions of hydroxyl group OH− with the corresponding emission bands in the 440 nm, 520 nm, and 600 nm regions. We have studied the dependence of the spectra
and the intensity of the photoluminescence for CsBr:Eu films on annealing temperature in air at 423–483 K, compared with analogous
dependences for CsBr:Eu single crystals obtained from the melt. We have shown that annealing the films at T = 423–463 K leads
to rapid formation of CsEuBr3 aggregate luminescence centers, while for T > 473 K thermal degradation of these centers occurs.
We conclude that the observed differences between the photoluminescence spectra of CsBr:Eu films and CsBr:Eu single crystals
may be due to additional doping of the films with OH− ions.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 191–194, March–April, 2006. 相似文献
13.
I. Kh. Abdukadyrova 《Journal of Applied Spectroscopy》2007,74(2):278-282
Features of the thermoradiative changes in the optical absorption and luminescence spectra of leucosapphire (colorless sapphire)
crystals irradiated by neutron fluences within the range 5·1015 to 5·1019 cm−2 have been studied in the visible region. The stepwise character of these processes was established as well as the basic steps
involved in bleaching the induced color of the wafers as a result of isochronal annealing. Some anomalies have been observed
in the temperature dependence of the optical density of the 460–620 nm bands, the activation energies for the color centers
as well as the color center concentrations have been calculated, and the nature of the radiation-induced centers has been
analyzed. An analytical expression is proposed to describe the accumulation kinetics for the centers during irradiation of
the crystals by reactor neutrons. It is concluded that there is an interconnection between, for example, the 460 nm color
centers and the 540 nm luminescence centers, and that there is a common mechanism for the process of radiation-induced defect
formation, initially responsible for their formation in the crystal. The possible effect of reabsorption of radiation on the
behavior of the Y(Φ) curve in the irradiated material is discussed.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 247–251, March–April, 2007. 相似文献
14.
N. N. Loshkareva Yu. P. Sukhorukov S. V. Naumov B. A. Gizhevskii G. N. Tatarinova T. A. Belykh 《Physics of the Solid State》1999,41(9):1433-1436
Long-range reduction of CuO to Cu2O and Cu was observed by irradiating polycrystals and different planes of CuO single crystals ((110) and (020)) with 16-MeV
nitrogen ions with fluence 1017 cm−2. The infrared absorption spectra show an increase in the number of hole [CuO4]5− and electronic [CuO4]7− centers. The highest density of electronic centers and reduction occur near the surfaces of the samples.
Fiz. Tverd. Tela (St. Petersburg) 41, 1564–1567 (September 1999) 相似文献
15.
A. P. Voitovich V. S. Kalinov G. Baldacchini R. M. Montereali M. Cremona 《Journal of Applied Spectroscopy》1998,65(5):778-795
Results of investigations of radiative F
3
+
-color centers in lithium fluoride obtained by the methods of one- and two-photon absorption, polarization spectroscopy, and
luminescence in singlet, triplet and triplet-singlet channels are reported. The scheme of energy levels of the F
3
+
-center is revised. The probabilities of singlet-triplet conversion and the rates of depletion of the lower triplet state
in the range of 80–350 K are presented. Recommendations are given on the technology of radiative LiF coloration that provide
an increase in the F
3
+
-center concentration and a decrease in the concentration of some other centers that prevent lasing on the LiF:F
3
+
active medium from being obtained. The phototransformations of color centers in LiF are analyzed. The parameters of lasers
with LiF:F
3
+
active media that provide generation of radiation tunable in the green region of the spectrum are considered. Based on spectroscopic
data the maximum attainable time characteristics of such lasers are discussed. The prospects for further investigations of
LiF:F
3
+
lasers are outlined in brief.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 745–760, September–October, 1998. 相似文献
16.
We have recorded and investigated the ESR spectrum of vanadium-doped α-RbTiOPO4 single crystals in the temperature interval 77–300 K. Two types of structurally distinct centers, V1 and V2, with a 4:1 ratio
of the peak intensities were observed. The angular dependences of the resonance magnetic fields are described by a spin Hamiltonian
corresponding to axial symmetry with the parameters g
∥1=1.9305, g
⊥1=1.9565, A
∥1=−168.2×10−4cm−1, and A
⊥1=−54.3×10−4cm−1 for V1 centers and g
∥2=1.9340, g
⊥2=1.9523, A
∥2=−169.0×10−4cm−1, and A
⊥2=−55.2×10−4cm−1 for V2 centers. A model of a paramagnetic center is proposed: The vanadium ions replace titanium ions in two structurally
distinct positions Ti1 and Ti2 (V1 and V2 centers, respectively). The possibility that a VO2+ ion forms when α-RbTiOPO4 crystals and crystals of the KTP group (KTiOPO4, NaTiOPO4, α-and β-LiTiOPO4), studied earlier, are doped with vanadium is discussed.
Fiz. Tverd. Tela (St. Petersburg) 40, 534–536 (March 1998) 相似文献
17.
V. Yu. Ivanov V. A. Pustovarov A. V. Kruzhalov D. S. Tausenev E. I. Zinin 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(4):671-674
The results of comparative luminescence investigation of natural and synthetic BeO crystals are presented. Time-resolved luminescence
(2.5–8 eV) and luminescence excitation spectra, and the kinetics of glow decay were measured using ultraviolet-vacuum-ultraviolet
(VUV) synchrotron radiation (5–22 eV) or x-radiation (50–620 eV or 3–62 keV) ranges. X-ray and thermostimulated luminescence
of natural BeO crystals were compared to the glow of additively colored synthetic crystals. The characteristic luminescence
of F and F
+ centers was found in natural crystals. In synthetic crystals similar luminescence is observed only after additive or radiation
coloration by virtue of the creation of F
− and F
+ centers on anion vacancies. The defects found in the crystal lattice of a natural BeO crystal testify to the degree of mineral
metamictization of the given deposit. 相似文献
18.
For an ensemble of different types of luminescence centers with overlapping absorption bands, with no restrictions on the
optical densities, we have obtained relations describing the luminescence excitation spectra for each type of center. We consider
transformations of the relations in some limiting cases. We suggest a procedure for using the equations obtained to determine
the characteristics of the luminescence centers. Some of these procedures have been experimentally implemented in study of
intrinsic radiation color centers in lithium fluoride crystals. We have determined the ratios of the luminescence quantum
yields for F2 and F3+ color centers, and we have observed that a major role is played by nonradiative transitions in deactivation of the first
excited singlet state of F3+ centers.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 365–371, May–June, 2008. 相似文献
19.
S. S. Novosad L. V. Kostyk I. S. Novosad I. M. Solskii 《Journal of Applied Spectroscopy》2010,77(5):728-731
We have studied thermally and photostimulated recombination processes in PbWO4 crystals in the temperature interval 90–295 K. We have shown that after x-ray excitation of the crystal at 90 K, the thermally
stimulated luminescence curve shows a relatively intense peak at 110 K and weak peaks at about 173, 191, and 232 K. Exposure
of the PbWO4 crystal to IR radiation after excitation by x-ray photons leads to the appearance of photostimulated flash luminescence,
a significant decrease in the intensity of the 110 K peak, and a shift of that peak to the 116 K region. But long-wavelength
illumination has less of an effect on the intensity and position of the higher temperature peaks. It is assumed that F− centers are formed in the PbWO4 crystal at 90 K during x-ray exposure. The thermal light sum released by IR illumination in the temperature region 90–150
K has a maximum at ≈108 K. The nature of this maximum is connected with the complex centers [Pb3+ + (WO3-F−)]. Optical and thermal degradation of these centers leads to the appearance of emission in the green region of the localized
exciton spectrum. 相似文献