共查询到20条相似文献,搜索用时 10 毫秒
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A. S. Shcheulin A. E. Angervaks T. S. Semenova L. F. Koryakina M. A. Petrova P. P. Fedorov V. M. Reiterov E. A. Garibin A. I. Ryskin 《Applied physics. B, Lasers and optics》2013,111(4):551-557
When growing CaF2 crystal doped with rare-earth ions, most of these ions are present in a trivalent state. However, due to contact with graphite crucible, a small proportion of a number of ions (Eu, Sm, Yb and Tm) are reduced to a bivalent state. A similar situation takes place during fabrication of CaF2 ceramics doped with rare-earth metals. This fact is of particular importance for laser CaF2:Yb crystals (ceramics), a promising material for short-pulse, high-power, high-energy diode-pumped solid state lasers since the presence of bivalent Yb ions can be a source of thermal losses. To date, there has been no technique to determine Yb2+ concentration in as-grown crystals. The proposed technique is based on a total reduction of Yb3+ ions via the heating of as-grown CaF2 crystals with known concentration of Yb in the reducing atmosphere of metal vapour and determining the cross section of absorption bands of Yb2+ ions. The knowledge of these parameters allows estimation of the Yb2+ content in CaF2:Yb crystals or ceramics by analysing their absorption spectra. Examples of using this technique are given. The technology of CdF2 crystals reduction (an “additive colouring”) and features of colouring of crystals doped with rare-earth ions are considered. 相似文献
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The absorption spectra of photochromic centers in CaF2, SrF2, and BaF2 crystals doped by La and Y impurities and thermal decay of the centers in the temperature range 80–600 K are investigated. Under low-temperature x-ray irradiation, ionized photochromic color (PC+) centers are generated in La- and Y-doped CaF2 crystals and in a La-doped SrF2 crystal. It is revealed that, upon heating of the CaF2-LaF3 crystal, PC+ centers are transformed into photochromic color (PC) centers. In the SrF2-YF3 crystal irradiated at room temperature, photochromic color centers are generated as well. All color centers decay at a temperature of approximately 600 K. After irradiation of the BaF2-YF3 crystal at a temperature of 80 K, absorption bands are observed at energies of 2.25 and 3.60 eV, which are related to neither PC centers nor PC+ centers. 相似文献
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Zavadovskaya K. K. Lisitsyn V. M. Fedorov V. A. Baranov A. I. 《Russian Physics Journal》1971,14(2):262-263
Russian Physics Journal - 相似文献
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A. S. Shcheulin T. S. Semenova A. E. Angervaks A. I. Ryskin 《Optics and Spectroscopy》2010,108(6):964-967
The study of the mechanism of additive coloring of calcium fluoride crystals, both pure and samarium-doped, demonstrates dynamical
nature of processes that, in the course of coloring, tend to maintain equilibrium between Sm3+ and Sm2+ ions. 相似文献
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Vorob'ev A. A. Zavadovskaya E. K. Lisitsyna L. A. Lisitsyn V. M. 《Russian Physics Journal》1969,12(4):454-460
A study of two types of additional absorption spectra observed in colored CaF2 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-nm band in synthesized CaF2 crystals. It is suggested that this band is due to defects produced in the lattice during the irradiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 12, No. 4, pp. 56–64, April, 1969. 相似文献
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S. S. Batsanov L. I. Kobets V. P. Kazakov L. R. Batsanova 《Journal of Applied Spectroscopy》1966,4(2):111-117
The luminescence and absorption spectra of fluorite crystals, alloyed with terbium fluorides, oxyfluorides, and oxides at concentrations of 0.01 to 5 mol.% were studied. The change in the optical spectra was studied as a function of the chemical composition of the alloy addition and also as a function of the concentration. It is proposed that the change with the concentration in the spectra of the crystals takes place as a consequence of mutual interactions between the ions with formation of cation pairs. It was observed that the ratio of the relative luminescence intensities of the crystals to the absorption coefficient changes nonlinearly with the concentration of the alloying addition. The problem of an interaction between an isomorphic admixture and crystal defects is discussed.In conclusion, the authors express their gratitude to E. V. Sobolev and M. V. Konovalova for help in the work. 相似文献
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The absorption in the vacuum and near ultraviolet region of CaF2 crystals containing lead and oxygen has been measured. Two main absorption bands at 155 and 202 nm are presumably due to lead centres and the band at 206 nm to oxygen. The nature of the weak band at 166 nm remains obscure. The absorption below 145 nm is probably due to excitons.The authors would like to express their gratitude to Ing. E.Mariani, CSc., for his interest and helpful discussions during the course of this work. 相似文献
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V. V. Kostin L. A. Kulevskii T. M. Murina A. M. Prokhorov A. A. Tikhonov 《Journal of Applied Spectroscopy》1967,6(1):19-20
These crystals produce 30 nsec pulses of peak power 1.4 MW in the single-pulse mode, or 40 nsec and 1 MW in the repetition mode (500 Hz repetition frequency). The beam produces a bright plasma when focused on the surface of a metal. 相似文献
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《Journal of Physics and Chemistry of Solids》1986,47(7):665-668
An ESR centre with orthorhombic symmetry was induced in CaF2:Gd crystals by X-ray irradiation after heat treatment at 900°C. The observed ESR spectrum has resolved shfs in particular crystal directions. Spin Hamiltonian analysis indicates that the ESR centre is a hole trapped at an oxygen substituted for a fluorine site and interacts mainly with two nearby fluorine ions located along the crystal [001] direction. The determined spin Hamiltonian parameters are gxx = 2.0036, gyy = 2.0159, gzz = 2.0306, Axx = 22.5, Ayy = 5.6 and Azz = 5.6 (G), respectively. A probable model is discussed by considering both the angular dependence of the ESR lines and the local charge neutrality around the ESR centre. 相似文献
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The electrical ionic conductivity of unirradiated and irradiated CaF2: Nd crystals in the range of 60 to 800°C has been measured. The conductivity plot is basically divided into four parts, i.e.,
intrinsic and extrinsic unassociated, extrinsic associated, and extrinsic segregated regions. Activation energy (for unirradiated
samples) in the extrinsic unassociated region is in the range of 0.69 to 1.20 eV depending on the doping concentration while
for the intrinsic region, it is of the order of 1.89 eV. The conductivity in the extrinsic unassociated region increases with
increase of Nd content in the sample. Also, the conductivity in the extrinsic region forγ-irradiated sample is higher than that for unirradiated one. In the intrinsic region, however, the conductivity is independent
of dopant concentration orγ-irradiation. From these results it is surmised thatF
− interstitials are the charge carriers in this region for CaF2: Nd3+ system. 相似文献
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Raman spectra of an Li2B4O7 crystal containing potassium and silver impurity ions with a concentration in a range of 0.1–0.2% were studied in detail. In the scattering geometries corresponding to manifestation of totally symmetric polar vibrations, the redistribution of spectral intensity for some lines in a region of 450–570 cm?1 was observed. Using the model of weakly interacting oscillators, parameters of vibrations in this region were determined. On the basis of present-day concepts of the theory of light scattering by impurities, the position of impurity ions in a crystal lattice is discussed. 相似文献