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1.
On the basis of studies of light-induced responses of doped lithium niobate crystals, a new approach to the spectroscopy of polar materials is developed. An experimental technique is described and possible applications and advantages of the approach are discussed. 相似文献
2.
Abstract The effect has been studied of additive coloring on the magnitude of ion conductivity of RbAg4I5 crystals. It has been found that slight changes of silver stoichiometry of 10?3 at.% can lead to considerable variations of the ionic conductivity Δ[sgrave]i/[sgrave]i ? 0.1. The dependence has been observed of the magnitude of ion conductivity on the ratio between the integral intensities of the main bands in the photoluminescence spectrum of the γ-phase of RbAg4I5 which associated with the luminescence centres containing vacancies and interstitials of silver cations. 相似文献
3.
M. Abarkan M. Aillerie J. P. Salvestrini M. D. Fontana E. P. Kokanyan 《Applied physics. B, Lasers and optics》2008,92(4):603-608
We report the optical and dielectric properties in hafnium (Hf)-doped lithium niobate (LN) crystals. We investigated samples
of congruent composition with various doping concentration varying from 0 to 8 mol%. The clamped and unclamped values of the
electro-optic coefficient r
22 of Hf-doped LN and the corresponding dielectric permittivity as well, have been experimentally determined and compared with
the results obtained in undoped congruent LN crystals. We show that the electro-optic and dielectric properties are only slightly
affected by the introduction of hafnium ions, and therefore Hf-doped LN has the advantage of low photorefractive damage compared
with the undoped congruent LN. 相似文献
4.
Ninel Kokanyan David Chapron Marc D. Fontana 《Applied Physics A: Materials Science & Processing》2014,117(3):1147-1152
The temperature dependence of the Raman spectrum in LiNbO \(_3\) is investigated from 100 to 700 K. The various sources of asymmetry of Raman bands and artefacts are discussed before analyzing the temperature dependence of A \(_1\) and E first-order phonon lines. The phonon frequency downshift and damping increase on heating are interpreted in terms of normal volume expansion and third- and fourth-order anharmonic potentials. Anharmonic contributions are highly anisotropic and mainly explain the temperature dependences of both frequency and damping of A \(_1\) optical vibrational modes along the ferroelectric axis. Results are consistent with Caciuc et al. (Phys Rev B 61:8806, 2000) predictions. 相似文献
5.
H. G. Demirkhanyan G. G. Demirkhanyan V. G. Babajanyan R. B. Kostanyan E. P. Kokanyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2008,43(1):13-18
Optical spectra of absorption and luminescence of LiNbO3:Yb3+ crystals are investigated experimentally and theoretically. Within the framework of the point charge approximation of crystal field, the Stark problem is solved: crystal field parameters and wave functions of Stark states are determined. Line strengths due to indirect electric-dipole and magnetic-dipole inter-Stark transitions are calculated and values of the Judd-Ofelt parameters are determined. Values of the branching ratios of luminescence. Einstein coefficients and, lifetime of the excited sublevel are calculated. A satisfactory agreement of calculated results with experimental data is obtained. 相似文献
6.
Sergey V. Shevchuk Natalia V. Rusakova Anna M. Turianskaya Yurii V. Korovin Ninel A. Nazarenko Andrey I. Gren 《Journal of fluorescence》1998,8(3):225-228
New ytterbium complexes with seven calix[4]resorcinarenes containing methoxycarbonyl, methyldiethylamino groups, and bromine as the substituents in the resorcinol ring and methyl or phenyl substituents in the macro ring were synthesized. The absorption, excitation, phosphorescence, and luminescence spectra of these complexes were studied. The positions of triplet levels of the ligands were measured and the values of relative quantum yields for the complexes were calculated. The paths of ligand–lanthanide energy transfer are discussed. 相似文献
7.
H. G. Demirkhanyan G. G. Demirkhanyan E. P. Kokanyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2017,52(4):381-386
The method of optical determination of temperature based on cooperative luminescence in the LiNbO3 crystals doped with rare earth ions is proposed. As a temperature-dependent measurable characteristic, the quantum yield of luminescence is considered taking into account the processes of nonradiative redistribution of the electron excitation energy in the impurity subsystem. It is shown that the LiNbO3–Yb3+ crystals can be used as a material for optical temperature sensors in the temperature range of 200–500 K with the average sensitivity of 0.12%K–1. 相似文献
8.
Okhrimchuk AG Butvina LN Dianov EM Lichkova NV Zagorodnev VN Boldyrev KN 《Optics letters》2008,33(19):2182-2184
A wideband near-IR (NIR) luminescence centered at 1080 nm was found in a RbPb(2)Cl(5):Bi single crystal grown by the Bridgman technique. Absorption, luminescence, and excitation of luminescence spectra were investigated at room and cryogenic temperatures. The luminescence was proposed to be due to the (3)P(1)-->(3)P(0) transition in Bi(+) ion. 相似文献
9.
G. G. Demirkhanyan E. P. Kokanyan H. G. Demirkhanyan D. Sardar M. Aillerie 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2016,51(1):28-34
The possibilities of LiNbO3-Ho3+ crystals for optical cooling based on the anti-Stokes luminescence in the wavelength range 2000-2200 nm are investigated. The efficiency and cooling temperature under the continuous wave (CW) excitation at the wavelengths 2035-2071 nm by ~100 W power are estimated. It is shown that under the CW excitation at 2035 nm wavelength the maximum cooling temperature is equal to 2.5 K, and at 2071 nm wavelength is equal to 10.9 K. 相似文献
10.
Alina Nicolescu Daniela Blanita Chiril Boiciuc Victoria Hlistun Mihaela Cristea Dorina Rotaru Ludmila Pinzari Ana Oglinda Adela Stamati Isabela Tarcomnicu Andreea Tutulan-Cunita Danae Stambouli Sergiu Gladun Ninel Revenco Natalia Uurelu Calin Deleanu 《Molecules (Basel, Switzerland)》2020,25(22)
The paper reports on monitoring methylmalonic aciduria (MMA)-specific and non-specific metabolites via NMR urinomics. Five patients have been monitored over periods of time; things involved were diet, medication and occasional episodes of failing to comply with prescribed diets. An extended dataset of targeted metabolites is presented, and correlations with the type of MMA are underlined. A survey of previous NMR studies on MMA is also presented. 相似文献