共查询到20条相似文献,搜索用时 11 毫秒
1.
V. M. Apatin V. O. Kompanets V. B. Laptev Yu. A. Matveets E. A. Ryabov S. V. Chekalin V. S. Letokhov 《JETP Letters》2004,80(2):95-97
It is found that CF 2HCl molecules dissociate under irradiation by high-intensity pulses of femtosecond radiation (λ=1.8 μm) in the vicinity of resonance with the frequency of overtone vibrational transitions in the C-H bond. It is shown that the dissociation products substantially differ from the products of dissociation of CF2HCl molecules from the ground and excited electronic states under the action of IR and UV nanosecond pulses. 相似文献
2.
P.?A.?Rodny? S.?D.?Gain I.?A.?Mironov E.?A.?Garibin A.?A.?Demidenko D.?M.?Seliverstov Yu.?I.?Gusev P.?P.?Fedorov S.?V.?Kuznetsov 《Physics of the Solid State》2010,52(9):1910-1914
Optical characteristics of BaF2 and BaF2: Ce single crystals and nanoceramic materials prepared from these single crystals by uniaxial hot pressing have been studied.
It has been shown that the introduction of Ce3+ ions into BaF2 hardly affects the ultrafast (∼0.9 ns) luminescence component. The integrated luminescence intensity of the BaF2: Ce nanoceramics is higher than that of the corresponding single crystal and considerably higher that the intensity of the
undoped BaF2 crystal. It has been demonstrated that the slow (several hundred nanoseconds) component of the luminescence decay of BaF2: Ce is due to the energy transfer from excitons to Ce3+ ions. 相似文献
3.
Vassiliki Katsika-Tsigourakou Efthimios S. Skordas 《Central European Journal of Physics》2010,8(6):900-904
Various experimental techniques have revealed that the predominant intrinsic point defects in BaF2 are anion Frenkel defects. Their formation, enthalpy and entropy, as well as the corresponding parameters for the fluorine
vacancy and fluorine interstitial motion have been determined. In addition, low temperature dielectric relaxation measurements
in BaF2doped with uranium leads to the parameters τ0, E in the Arrhenius relation τ = τ0 exp(E/k
B
T) for the relaxation time τ. For the relaxation peak associated with a single tetravalent uranium, the migration entropy deduced
from the pre-exponential factor τ0 is smaller than the anion Frenkel defect formation entropy by almost two orders of magnitude. We show that, despite their
great variation, the defect entropies and enthalpies are interconnected through a model based on anharmonic properties of
the bulk material which have been recently studied by employing density-functional theory and density-functional perturbation
theory. 相似文献
4.
P. Camy J.L. Doualan A. Benayad M. von Edlinger V. Ménard R. Moncorgé 《Applied physics. B, Lasers and optics》2007,89(4):539-542
We present the spectroscopic properties and room-temperature cw tunable laser operation of Yb3+-doped CaF2, SrF2 and BaF2 single crystals grown and studied in the same conditions. Emission cross sections, lifetimes, laser thresholds, laser slope
efficiencies and laser wavelength tuning ranges are compared. It appears that Yb3+-doped BaF2 might be more promising for diode-pumped high power laser operation.
PACS 42.55.Rz; 42.70.Hj 相似文献
5.
The location of the energy levels of rare-earth (RE) elements in the energy band diagram of BaF2 and CdF2 crystals is determined. The role of RE 3+ and RE 2+ ions in the capture of charge carriers, luminescence, and the formation of radiation defects is evaluated. It is shown that the substantial difference in the luminescence properties of BaF2: RE and CdF2: RE is associated with the location of the excited energy levels in the band diagram of the crystals. 相似文献
6.
V. O. Kompanets V. B. Laptev A. A. Makarov S. V. Pigulsky E. A. Ryabov S. V. Chekalin 《JETP Letters》2010,92(3):135-139
The dynamics of multiphoton excitation of (CF3)2CCO molecules has been investigated under the condition of resonant action of femtosecond infrared laser radiation on the
ν1 vibrational mode of the C=C=O bond. It has been shown that the mode-selective excitation of this vibration occurs up to the
ν = 6 level. The kinetics of the subsequent intramolecular vibrational energy redistribution from the ν1 mode has been measured. A value of 5 ± 0.3 ps has been obtained for the characteristic time of this process. 相似文献
7.
8.
This paper reports on the spectroscopic properties and energy transfer analysis of Tm3+-doped BaF2-Ga2O3-GeO2-La2O3 glasses with different Tm2O3 doping concentrations (0.2, 0.5, 2.0, 2.5, 3.0, 3.5, 3.5, 4.0 wt%). Mid-IR fluorescence intensities in the range of 1,300 nm−2,200 nm
have been measured when excited under an 808 nm LD for all the samples with the same pump power. Energy level structure and
Judd-Ofelt parameters have been calculated based on the absorption spectra of Tm3+, cross-relaxation rates and multi-phonon relaxation rates have been estimated with different Tm2O3 doping concentrations. The maximum fluorescence intensity at around 1.8 μm has been obtained in Tm2O3-3 wt% sample and the maximum value of calculated stimulated emission cross-section of Tm3+ in this sample is about 0.48 × 10−20 cm2 at 1,793 nm, and there is not any crystallization peak in the DSC curve of this sample, which indicate the potential utility
of Tm3+-doped BaF2-Ga2O3-GeO2- La2O3 glass for 2.0-μm optical fiber laser. 相似文献
9.
Atomically smooth CaF2 and BaF2 layers have been sequentially grown on Si(111) substrates by molecular beam epitaxy. Pore macrodefects have been revealed at the points of the action of an electron beam from a diffractometer when analyzing the crystal structure of the surface during the growth with the subsequent observation using atomic force microscopy. The formation of these macrodefects is associated with the decomposition of fluorides by high-energy electrons, which is accompanied by the desorption of fluorine and the drift current of positive ions from the electron charge drains. 相似文献
10.
E. R. Zhiteitsev V. A. Ulanov M. M. Zaripov E. P. Zheglov 《Physics of the Solid State》2005,47(7):1254-1257
Tetragonal paramagnetic centers with spin S = 7/2 were detected in x-ray-irradiated BaF2: Fe (cFe ≈ 0.002 at. %) crystals using the EPR method. Electronic transitions between the |±1/2〉 states of a Kramers doublet were observed in the X and Q ranges. In the EPR spectra of the tetragonal centers, a ligand hyperfine structure (LHFS) was observed corresponding to the interaction of the electron magnetic moment of the tetragonal center with eight equivalent ligands. The large spin moment, significant anisotropy of the magnetic properties, and the characteristic LHFS indicate that the tetragonal center is a Fe1.5+?Fe1.5+ dimer in which the two iron ions are bound via superexchange interaction. It is assumed that, before crystal irradiation, this dimer was in the Fe3+(3d5)?Fe+(3d7) state. 相似文献
11.
The initiation of H2/O2/H2O mixture combustion when asymmetric vibrations in H2O molecules are excited by a resonant IR laser radiation is considered. It is shown that the vibrational excitation of the molecules gives rise to new efficient channels for the formation of chemically active O and H atoms and OH radicals. As a result, the chain mechanism of combustion in the mixtures is enhanced and, as a consequence, the induction time is cut and the ignition temperature is lowered. Even at a minor radiant energy flux delivered to the gas (Ein≈2.5 J/cm2), the ignition temperature of the stoichiometric H2/O2 mixture containing only 5% of H2O may become as low as 300 K. 相似文献
12.
Yu. A. Kotov V. V. Osipov O. M. Samatov M. G. Ivanov V. V. Platonov A. M. Murzakaev E. I. Azarkevich A. I. Medvedev A. K. Shtolts O. R. Timoshenkova 《Technical Physics》2004,49(3):352-357
The characteristics (phase composition, grain shape, grain size distribution, and specific surface area) of Ce0.78Gd0.22O2-δ nanopowders produced by exposing the target to pulsed CO2 laser radiation are reported. Reasons for a threefold increase in the output of the experimental powder-preparation unit
(up to 60 g/h) with the characteristic grain size (≈10 nm) remaining unchanged are discussed. 相似文献
13.
Amin Heshmati-Moulai Hamidreza Simchi Mahdi Esmaeilzadeh 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(7):128
We study perfect valley polarization in a molybdenum disulfide (MoS2) nanoribbon monolayer using two bands Hamiltonian model and non-equilibrium Green’s function method. The device consists of a one-dimensional quantum wire of MoS2 monolayer sandwiched between two zigzag MoS2 nanoribbons such that the sites A and B of the honeycomb lattice are constructed by the molecular orbital of Mo atoms, only. Spin-valley coupling is seen in energy dispersion curve due to the inversion asymmetry and time-reversal symmetry. Although, the time reversal symmetry is broken by applying an external magnetic field, the valley polarization is very small. A valley polarization equal to 46% can be achieved using an exchange field of 0.13 eV. It is shown that a particular spin-valley combination with perfect valley polarization can be selected based on a given set of exchange field and gate voltage as input parameters. Therefore, the valley polarization can be detected by detecting the spin degree of freedom. 相似文献
14.
D.W. Ward E.R. Statz K.A. Nelson 《Applied Physics A: Materials Science & Processing》2007,86(1):49-54
Fabrication of patterned materials in ferroelectric LiNbO3 and LiTaO3 crystals using femtosecond laser micromachining is presented and discussed. Damage feature sizes in the 10–100 μm range were achieved using 800-nm, 50-fs (FWHM) ultra-fast laser pulses with energies ranging from 10 μJ up to 350 μJ. Fabrication of polaritonic devices such as waveguides, resonators, focusing reflectors, diffractive and dispersive elements, photonic band gap materials, and other microstructures is demonstrated. PACS 77.84.Dy; 42.62.Cf; 71.36.+c 相似文献
15.
Yu. M. Andreev A. A. Ionin I. O. Kinyaevskii Yu. M. Klimachev A. Yu. Kozlov A. A. Kotkov G. V. Lanskii 《Bulletin of the Lebedev Physics Institute》2010,37(1):11-12
The experimental results of the study of CO laser frequency doubling in ZnGeP2 and GaSe nonlinear crystals of high optical quality are presented. A multifrequency low-pressure Q-switched CO laser and
a selective pulsed electroionization mode-locked CO laser with cryogenic cooling were used in the experiments. The highest
external factor of radiation conversion into the second harmonic of the pulse-periodic Q-switched CO laser and pulsed mode-locked
CO laser was 1% and 3.5%, respectively. Theoretical calculations showed the possibility of obtaining far IR and terahertz
radiation using difference frequency generation of CO laser lines in these crystals. 相似文献
16.
V. Romano M. Meier N. D. Theodore D. K. Marble M.-A. Nicolet 《Applied Physics A: Materials Science & Processing》2011,104(1):357-364
Films of 260 nm thickness, with atomic composition Ta42Si13N45, on 4″ silicon wafers, have been irradiated in air with single laser pulses of 200 femtoseconds duration and 800 nm wave
length. As sputter-deposited, the films are structurally amorphous. A laterally truncated Gaussian beam with a near-uniform
fluence of ∼0.6 J/cm2 incident normally on such a film ablates 23 nm of the film. Cross-sectional transmission electron micrographs show that the
surface of the remaining film is smooth and flat on a long-range scale, but contains densely distributed sharp nanoprotrusions
that sometimes surpass the height of the original surface. Dark field micrographs of the remaining material show no nanograins.
Neither does glancing angle X-ray diffraction with a beam illuminating many diffraction spots. By all evidence, the remaining
film remains amorphous after the pulsed femtosecond irradiation. 相似文献
17.
The nonlinear microwave absorption in the (CH3NH3)2CuBr4 antiferromagnetic crystal is investigated experimentally. The temperature and angular dependences of the parameters of nonlinear resonance and the dependences of these parameters on the microwave pump power are analyzed. It is found that the nonlinear properties deteriorate with decreasing temperature and the linear and nonlinear contributions are competitive in character. 相似文献
18.
N. I. Filimonova V. A. Ilyushin A. A. Velichko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2017,11(1):130-134
The surface morphology of BaF2 epitaxial films grown by MBE (molecular beam epitaxy) in various modes on the surface of CaF2/Si(100) is investigated by AFM. The CaF2 layers on Si(100) are obtained in the high-temperature growth mode (Т S = 750°C). It is shown that the epitaxy of BaF2 at a temperature of 600°C at the initial stage of growth leads to the formation of defects such as perforations in the epitaxial film, while epitaxy at a temperature of 750°C provides a defect-free film with a surface morphology suitable for the subsequent growth of semiconductors of IV–VI type and solid solutions based on them. 相似文献
19.
L. N. Korotkov T. N. Korotkova R. R. Levitskii S. I. Sorokov A. S. Vdovych 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(10):1331-1334
The time dependences of polarization of K0.88(NH4)0.12H2PO4 mixed crystal have been studied within the temperature range of 74–100 K. Two mechanisms of polarization relaxation were
found. The first mechanism is caused by domain walls lateral motion and their interaction with point lattice defects. The
second one supposedly is due to polar regions infiltration through the regions of frustrated paraelectric phase. 相似文献
20.
Using a very simple and straightforward approach we derive the condition to be satisfied for achieving wavelength-insensitive broadband phase matching in a type-I noncollinear optical parametric amplifier (NOPA), required for the generation of ultra-fast laser radiation. Nonlinear optical properties of a relatively newly grown crystal Li2B4O7 (LB4) have also been studied and we found that this crystal satisfies the condition required to realize the broadband phase matching and is suited for the generation of tunable visible–near-infrared ultra-fast laser radiation employed in a 395-nm-pumped type-I NOPA. The phase-matching bandwidths of type-I NOPAs in different borate-group crystals, such as BBO, CLBO, and KABO, are also numerically estimated. The values are 157, 164, 152, and 174 THz for 1-mm-thick BBO, CLBO, KABO, and LB4 crystals, with the noncollinear angles between the input pump and the signal beams 3.7°, 3.0°, 3.4°, and 2.9°, respectively, for the signal wavelengths centered at 630 nm. In addition to the largest bandwidth, LB4 crystal has several other attractive properties to be used in optical parametric applications, such as high laser damage threshold, wide optical transmission, easy crystal growth to excellent optical quality with large sizes, easy treatment of cutting and polishing, and nonhygroscopicity. PACS 42.65.Yj; 42.65.Re; 42.70.Mp 相似文献