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1.
The 2000 Å absorption system in the benzene single crystal is investigated at liquid nitrogen temperature. The analysis of the polarized spectra recorded along b and c in (100) plates appears to be not in favour of the assignment of the π* └π system to an upper state of B 1u symmetry, and it is not in contrast with the hypothesis of a 1 E 2g upper state. The first band in the system, located at 46 565 cm-1, and totally polarized along c, is discussed in terms either of an out-of-plane false origin of the 1 E 2g └1 A 1g system, or of a new transition lying between the first two well known π-systems of benzene, possibly of π* └σ type. 相似文献
2.
The Roothaan open-shell LCAO-MO-SCF method was coupled with the Simons model potential in calculations of internuclear distances and ionization potentials for Li3, Na3, K3, Rb3, and Cs3 taking core polarization into account. 相似文献
3.
S. Bernhardt H. Veenhuis P. Delaye R. Pankrath G. Roosen 《Applied physics. B, Lasers and optics》2001,72(6):667-675
We present an experimental investigation of the photorefractive properties of rhodium-doped barium calcium titanate (BCT) crystals of the congruent melting composition Ba0.77Ca0.23TiO3. Considering the results previously obtained on this crystal in the visible region, it should be a good alternative to BaTiO3. Nevertheless, many applications use infrared light. Therefore we present here a study of rhodium-doped BCT crystals at 850 nm. This wavelength is of special interest as it is in the spectral range of laser diodes. Rhodium doping is expected to enhance the sensitivity of the crystal in the infrared as is the case for BaTiO3.We first noticed that BCT:Rh crystals are sensitive at this wavelength as expected. Furthermore, the photorefractive properties are interesting in terms of photorefractive gain, with a gain as high as 3 cm-1 with ordinary polarization. This study has also put forward the fact that rhodium is not the only defect that participates in the photorefractive effect. Indeed, a large quantity of iron seems to be present in the BCT crystals and to participate in the photorefractive effect.An Erratum to this article can be found at 相似文献
4.
V. V. Shpeizman N. N. Peschanskaya V. M. Egorov V. I. Nikolaev B. I. Smirnov R. K. Nikolaev 《Physics of the Solid State》1999,41(6):1017-1020
The temperature spectrum of small-inelastic-strain rates in a vapor-phase-grown C60 single crystal has been measured within the 200–290 K interval with a high-precision strain-rate meter based on a laser interferometer.
The spectrum exhibits a strong peak in the region of the phase transition at 250–260 K and a slight strain acceleration at
∼240 K, which correlates well with the calorimetric curve. The first maximum is associated with strain that developes more
easily in an fcc than in a primitive cubic lattice, and the second, to the effect on the strain rate of annealing of the defects
created with fast crystal heating.
Fiz. Tverd. Tela (St. Petersburg) 41, 1115–1118 (June 1999) 相似文献
5.
Y. Kato E. Miura T. Tachi H. Shiraga H. Nishimura H. Daido M. Yamanaka T. Jitsuno M. Takagi P. R. Herman H. Takabe S. Nakai C. Yamanaka M. H. Key G. J. Tallents S. J. Rose P. T. Rumsby 《Applied physics. B, Lasers and optics》1990,50(4):247-256
Planer stripe and foil targets coated with NaF were irradiated with high intensity 351 nm laser radiation of 130 ps duration. Time-integrated as well as time-resolved measurement of gain on NaXIH at 54.2Å were made. A time-integrated gain of 1.2
–1.1
+0.8
cm–1 and a time-resolved peak gain of 3.2±1.0 cm–1 were obtained. A detailed account of the experimental procedures for determination of gain is given. 相似文献
6.
The first π*←π transition in the benzene single crystal is investigated at 82 K. Intensities and polarization ratios for both true and false origins in crystal planes (100) and (010) have been measured and rationalized in terms of crystal field perturbation. At liquid nitrogen temperature the origin of the transition is located at 37865 cm-1 (b), 37817 cm-1 (c) and 37807 cm-1(a). 相似文献
7.
A polarization-type saturated absorption spectrum set-up for {}^{87}Rb atom laser cooling and trapping has been established in our laboratory. By changing the polarization components and optical power, enhanced absorption of the transition 5S_{1/2} F=2→5P_{3/2}F′=3 was observed with other transitions and cross-over resonance staying unvaried. 相似文献
8.
《Journal of Molecular Spectroscopy》1987,123(1):126-134
The D2O absorption spectrum recorded with a selective modulation Girard spectrometer in the region of 3690–4190 cm−1 (resolution ∼0.07 cm−1) has been analyzed. Based on the fitting of experimental data the spectroscopic parameters of the vibrational state (011) have been determined and the parameters of the vibrational states (110) and (030) have been estimated. 相似文献
9.
《Journal of Molecular Spectroscopy》1987,125(2):393-412
Ionization-detected stimulated Raman spectroscopy was used to obtain high-resolution recordings of the two perpendicular bands of the benzene molecule centered at 1591.327 and 1609.518 cm−1. The effective resolution was further enhanced by deconvolving the spectrum to a linewidth 0.003 to 0.004 cm−1. Fine-tuning of the ionizing radiation made it possible to record the transitions belonging to each band separately, thus greatly simplifying the spectrum in the region of overlap. The strong sS and oO branches were, for the most part, completely resolved as were many lines in the weaker oP and sR branches and even in the central oQ and sQ branches. The observed bands belong to the E2g fundamental ν16 in nearly exact Fermi resonance with the combination ν2 + ν18. A detailed rovibrational analysis of the spectrum is reported. A perturbation detected in the sSk branches of the lower-frequency band for K = 19 to 23 was identified as a quintic anharmonic resonance with the third overtone, 4ν20, of the lowest lying fundamental ν20, which is infrared- and Raman-inactive (species E2u). Deperturbed spectroscopic constants for the interacting states are reported which reproduce the observed line positions with a standard deviation of 0.0013 cm−1. The unperturbed origins of the ν16 and ν2 + ν18 states are only 1.106 cm−1 apart. The fundamental ν16 was identified with the higher-frequency state with origin at 1600.976 cm−1. 相似文献
10.
Polarized positrons can be generated through the electron-positron pair creation from circularly polarized gamma-rays hitting a conversion target. Laser-Compton scattering is an efficient method to generate circularly polarized gamma-rays. Simulation studies on these two processes have been done with the Monte Carlo codes, CAIN and GEANT4. Using CAIN to simulate the Laser-Compton scattering process, the energy spectrum of the generated polarized photons could be obtained. GEANT4 was used to study the yield, energy spectrum and the mean polarization of the positrons emanating from the conversion target. To increase the yield of the generated positrons, an optimization study on the thickness of conversion target was also performed. 相似文献
11.
P. Lakshmi Praveen 《Phase Transitions》2013,86(5):515-525
The electronic transitions in the ultraviolet–visible (UV–Vis) range of two nematogens, namely 4′-cyanophenyl-4-n-pentylbenzoate and 4′-cyanophenyl-4-n-pentoxybenzoate, have been studied. The UV–Vis and circular dichroism spectra of these molecules have been simulated using the TDDFT/B3LYP/6-31+G(d) method. Mulliken atomic charges for each molecule have been compared with Loewdin atomic charges to analyze the molecular charge distribution and phase stability. The highest occupied molecular orbital and lowest unoccupied molecular orbital energies corresponding to the electronic transitions in the UV–Vis range have been reported. The excited states have been calculated via configuration interaction singles with semi-empirical Hamiltonian ZINDO (Zerner's intermediate neglect of differential overlap method). Further, the effect of substituent on ultraviolet absorption and photostability of the molecules has been discussed. The photostability of the molecules has been investigated in order to understand the application and operation with ultraviolet and visible light regions. 相似文献
12.
G. G. Bunatyan 《Journal of Experimental and Theoretical Physics》1999,89(5):811-820
Since the emission of γ grays unavoidably accompanies β decay, the final state after the β decay of a neutron includes a photon along with a proton, an electron, and an antineutrino, i.e., four particles, rather
than three. Therefore, when only the electron and proton momenta are detected and the γ-ray momentum is not detected in an experiment, the antineutrino momentum cannot be uniquely reconstructed, and only its mean
value over a γ-ray momentum distribution determined from corresponding calculations can be considered. The γ grays are significant for finding the asymmetry parameter B of the antineutrino angular distribution from experiments on the β decay of polarized neutrons, where the electron momentum p directed along the x axis and the projection of the proton momentum P
x onto the x axis are detected, and the neutron polarization vector ξ is parallel or antiparallel to x. Since the γ rays are not detected in such experiments, the antineutrino kinematics are not uniquely specified by the observables p and P
x and can be reconstructed only on the average, so that the antineutrino momentum distribution averaged over a γ-ray momentum distribution is considered. Thus, the exact value of B cannot be obtained from these experiments, but the true value of B can be estimated on the average by considering the mean (most likely) value 〈B〉 and the dispersion (rms deviation) ΔB. The unavoidable uncertainty in the estimate of B amounts to several percent and is thus significant for present-day experiments, which are intended to obtain the value of
B to a very high accuracy of ∼ (0.1–1)%. If electromagnetic interactions are taken into account, measurements of the electron
and proton momentum distributions can also be used to obtain g
A, i.e., the axial β-decay amplitude, to high accuracy.
Zh. éksp. Teor. Fiz. 116, 1505–1522 (November 1999) 相似文献
13.
A. A. Saafan A. A. El-Barbary M. A. Sakran A. I. Khodair 《Isotopes in environmental and health studies》2013,49(4):181-186
A number of 1,3-diphenyl-2-thiohydantoin azo dyes were purely prepared and characterized by spectroscopic analyses. Then the azo dyes were subjected to γ-radiation doses of up to 109 rd. Results obtained indicated that the spectral bands of the investigated azo dyes suffer shifts, changes in intensity, broadening, creation of new bands and/or completely disappearance of others as a result of radiation damage. Furthermore a sequence for the relative stability of the different dyes towards gamma radiation damage was put forward. 相似文献
14.
V. M. Egorov V. I. Nikolaev B. I. Smirnov V. V. Shpeizman R. K. Nikolaev 《Physics of the Solid State》1999,41(3):494-496
A thermodynamic transition in C60 crystals, subjected beforehand to uniaxial compression at various temperatures and to thermal action, was investigated by
differential scanning calorimetry. It was established that compression of the crystal at temperatures below the phase transition
has a much smaller effect on the transition itself than a similar or even much weaker action at a temperature above the phase
transition. A “quenching” effect was also found. This effect is probably due to the orientational order of individual fullerene
molecules. A correlation was established between the magnitude of the effect and the preliminary deformation of C60 crystals.
Fiz. Tverd. Tela (St. Petersburg) 41, 550–553 (March 1999) 相似文献
15.
G. G. Bunatian 《JETP Letters》1999,69(10):728-733
In experiments on the β decay of polarized neutrons where only the electron and proton momentum distributions are observed and the γ radiation is not registered, the asymmetry factor B of the antineutrino angular distribution cannot be obtained rigorously — the value of B is only estimated on the average by taking into consideration the expectation (mean) value 〈B〉 and the rms deviation ΔB. The resulting unavoidable ambiguities in the determination of B amount to several percent, which is significant for the present-day experimental attempts to obtain B to very high precision ∼(0.1–1)%.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 10, 681–685 (25 May 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
16.
《Physics letters. [Part B]》1988,213(2):195-202
We have studied the eigenvalues of the Wilson fermion matrix on various lattice sizes and for a range of coupling constants, β, in the quenched approximation. The implications for the phase structure of lattice QCD in the presence of Wilson fermions are discussed. 相似文献
17.
I. G. Kuleev I. I. Kuleev A. V. Inyushkin V. I. Ozhogin 《Journal of Experimental and Theoretical Physics》2005,101(2):322-330
The Zeeman effect, magnetization M(H), and differential magnetic susceptibility dM/dH of ErVO4 crystals in a pulsed magnetic field have been experimentally and theoretically studied. In magnetic fields H ∥ [001] and H ∥ [100], the energy levels of Er3+ ions exhibit mutual approach and crossing (the crossover effect), which results in the peaks in dM/dH and the jumps in M(H) curves at low temperatures. The anomalies in the magnetic properties related to the crossover in ErVO4 for H ∥ [001] are highly sensitive to the electronic structure of Er3+ ion, which allows this effect to be used for refining the crystal field parameters. The influence of the temperature, field misorientation from the symmetry axis, parameters of pair interactions, and other factors on the magnitude and character of magnetic anomalies in ErVO4 crystals is considered. 相似文献
18.
Davis-Mott and Tauc models of optical absorption at the absorption edge in the high absorption coefficient region (104cm–1) are carefully reviewed with regard to their theoretical foundations, assumptions, mathematical derivations, and results. The full implications of these models are exploited, and it is found that the Davis-Mott model for negligible matrix elements between localised states could account for the cubic power law behaviour of with photon energy of some amorphous semiconductors such as a-Si. A fractional power law to find the optical band gapE
opt, of the form [ (–E
opt)r; 2r3] based on Davis-Mott model is proposed in which the indexr can be a function of disorder. The Tauc model has further been extended to the case of negligible matrix elements between localised states, in which the same square power law for vs. with the same meaning of the optical gap as in the original Tauc model has resulted. A consideration of the case of unequal matrix elements for those transitions between localised states and those between extended states is also included. The meaning ofE
opt has been re-assessed and it is emphasized that it is an extrapolation of delocalised states to the zero of the density of states rather than a threshold energy for the onset of some kind of optical transitions.This paper is cordially dedicated to Professor C. A. Hogarth who taught us the Physics of amorphous materials. 相似文献
19.
20.
《Journal of Quantitative Spectroscopy & Radiative Transfer》1986,35(6):495-499
Measurements of pressure broadened half-widths have been performed for one vibration-rotation line in the 6190Åmethane band and one vibration-rotation line in the 6825Åmethane band. Self-, nitrogen-, hydrogen- and helium-broadening have been measured over a temperature range of 77–295 K. Pressure broadening coefficients and temperature dependence indices have been obtained for each line and broadening gas. 相似文献