共查询到20条相似文献,搜索用时 31 毫秒
1.
Long wavelength optical phonons of quartz were analyzed by a Born-Von Karman model not previously used. It was found that only one force constant associated with the turning of the Si-O bonds has a critical effect on the soft-mode frequency and the α-β transition in quartz. The square of the soft-mode frequency was found to depend linearly on this force constant which has the temperature dependence in units of 104 dyn/cm2. 相似文献
2.
Experimental evidence is presented in support of the validity of the hypothesis of two-scale-factor universality for the correlation function of fluids near the gas-liquid critical point. For Xe, SF6, and CO2, the dimensionless quantity is universal within the experimental accuracy of 10% and agrees with the value predicted by theory. 相似文献
3.
On the basis of expansion, the critical amplitude for specific heat is shown to be discontinuous at space dimensions . This property is confirmed up to the order of . 相似文献
4.
H.H. Bolotin D.L. Kennedy B.J. Linard A.E. Stuchbery S.H. Sie I. Katayama H. Sakai 《Nuclear Physics A》1979,321(1):231-249
The lifetimes of five excited states in 197Au up to an excitation energy of 885 keV were measured by the recoil-distance method (RDM). These levels were populated by Coulomb excitation using both 90 MeV 20Ne and 120 MeV 35Cl ion beams. The experimentally determined spectroscopy of the low-lying levels (ground state) and , , , and at 77.3, 268.8, 278.9, and 547.5 keV excitation energy, respectively, has been critically compared with the detailed predictions of the de-Shalit weak-coupling core-excitation model. When the model is taken to represent the case of a proton hole coupled to a 198Hg core, the model parameters obtained are in accord with the criteria implicit for weak core coupling and, at the same time, are in remarkably good agreement with virtually all measured E2 and M1 transition rates. 相似文献
5.
Y. Yosida 《Physics letters. A》1978,65(2):161-162
Intensity decrease of the Rayleigh scattered light in a critical mixture of cyclohexane-methanol was observed in the temperature range with ac electric field applied. 相似文献
6.
J.F. Seely R.H. Dixon R.C. Elton J.G. Lunney 《Journal of Quantitative Spectroscopy & Radiative Transfer》1982,27(3):297-306
The Lyman-α and adjacent dielectronic satellite lines have been observed in the spectra from laser-irradiated solid targets. In a carbon plasma from a planar target, the relative intensity of the satellite line of C(V) increases as a function of electron density in the range 8 × 1019 to 2 × 1020 cm?3. As analysis of a series of imploded microballoon experiments indicates that the and satellite radiation of Si(XIII) increases for electron densities 1 × 1022?2 × 1023 cm?3. The satellite intensity distributions have been numerically simulated using a rate equation model. It is shown that the carbon and silicon satellite data may be interpreted in a consistent manner, and the extension to higher atomic numbers Z and higher electron densities is considered. 相似文献
7.
I.O. Kulik 《Physics letters. A》1984,106(4):187-190
For metals with small electron and phonon mean free paths (alloys, deformed or amorphous materials), there exists a possibility of determining α2F(ω) by measuring the V dependence of or of wide (d ? 103 Å) point contacts (PC) and then inverting the linear equation relating these quantities to α2F(ω). The procedure is elaborated numerically and tested successfully for model electron-phonon interaction spectra. 相似文献
8.
Flow birefringence is examined in classical fluids near the critical point under oscillating incompressible flows. This effect originates from anisotropy in the fluctuation part of the dielectric tensor in the presence of a flow and is found to be enhanced near the critical point. When the flow is stationary, the birefringence phase shift δ is proportional to ξ2D in the weak shear regime and to in the strong shear regime where ξ is the correlation length and D is the shear rate. For the oscillatory case we examine only the weak shear regime. One characteristic feature is that δ becomes independent of T ? Tc when the frequency of the flow exceeds the average decay rate of critical fluctuations. 相似文献
9.
Metastable 23S1 He atoms are optically oriented and their orientation is transferred to metallic ions produced by Penning collisions . If r.f. transitions are induced in the 23S1 He level, the circularly polarized light emitted by the ions in a direction perpendicular to the static magnetic field is modulated at the r.f. frequency. The variation of the modulation amplitude with frequency depends on the lifetime of the level of the excited ion.We describe an experimental apparatus with which we measure the modulation amplitude from 1 MHz to 110 MHz. In this way the lifetime of the 4f2F and 2F Mg+ levels has been determined. 相似文献
10.
Experimental data concerning the electrical conduction and Hall coefficient in HgTe samples with acceptor states have been collected and analysed. In the analysis three ranges of acceptor concentration have been distinguished: a low concentration range up to about 5 × 1015 cm?3 (pure samples), a high concentration range from 1016 to 1018 cm?3 (p-like samples), and an extremely high concentration range above 1018 cm?3 (p-type samples). In pure HgTe samples the holes are in the valence band, in p-like samples the “holes” are in the impurity band, and in p-type HgTe samples the holes are in a strong mixing impurity-valence band. The mobility of holes in the valence band is of the order of . The mobility of “holes” in the impurity band decreases with increasing impurity concentration from about to . The mobility of holes in p-type HgTe samples is independent of the acceptor concentration and is equal to . 相似文献
11.
The results of measurements for pentane solutions of o-nitrotoluene near their critical temperature are presented. The value for the critical solution (f=0.36) is positive and greater than for pure o-nitrotoluene, which is attributed to the interaction of concentration fluctuations with the electric field. 相似文献
12.
The rise time of the near-infrared fluorescence intensity has been measured in YAG:Nd3+ at room temperature under the excitation by 10 ns duration pulses at 514.5 nm using a time-correlated single photon counting method. The result reveals that the relaxation rate from the pumped level ( + + to the upper level laser level is larger than 108s?1, which is in contrast with the previously reported values of (1.6 ~ 2) × 106s?1. An experiment to search for the visible emission in YAG:Nd3+ gives support to the present value. 相似文献
13.
The behaviour of the transport coefficients of a Van der Waals fluid is studied in the one-phase region along the critical isochore of the liquid-vapour phase transition. When the strongest singularity is found in the case of the bulk viscosity (???2). The divergence of the heat conductivity is shown to be weaker than . The shear viscosity tends to a finite limit. The coefficients of the asymptotic laws are explicitly given. All the results are established in the region where the Ornstein-Zernike theory applies. 相似文献
14.
M. Villedieu N. Devismes A.M. de Goër 《Journal of Physics and Chemistry of Solids》1977,38(9):1063-1070
The effect of γ irradiation at 300 K on the concentrations of vanadium ions V3+, V4+ and V2+ in Al2O3 has been studied quantitatively, using three techniques: optical absorption (V3+), low temperature thermal conductivity measurements (V4+) and EPR (V2+). Several single crystals of Al2O3 doped with vanadium in a large range of concentration have been measured. The evolution of the respective concentrations by γ irradiation as a function of the total vanadium content C is quite different in the two regions and C larger than this value. A consistent analysis of the results has nevertheless been achieved, leading to the determination of the absolute concentrations of the three ions in the as-received and γ irradiated states for all samples with (room temperature annealing is observed above this value). The concentrations of V4+ and V2+ ions are always small, but V4+ ions are more stable: they are present in the as-received state at a level of 1% of the total concentration and a maximum value of is observed in the γ irradiated state; on the other hand there are less than 4.7 × 1015V2+ ions per cm3 in the as-received state and the maximum value is only . Charge transfer between V ions only is not sufficient to explain the experimental results and other defects must be involved in the γ irradiation effect. 相似文献
15.
D. Yaffe M. Abramovich V. Chaloupka A. Ferrando M. Korkea-aho M.J. Losty L. Montanet E. Paul J. Zatz Z. Zieminski 《Nuclear Physics B》1974,75(3):365-387
We have investigated the final states K10(890)Σ, and K10(890) Y110(1385) produced in π?p interactions at 3.93 GeV/c. We present the differential cross sections and spin density matrix elements for the resonances as functions of momentum transfer, as well as the gL and Σ0 polarizations. The Σ0 polarization is found to be positive and maximal. An amplitude analysis is performed for the K1 Λ and reactions, and it is found that one natural parity transversity amplitude is dominant for the latter. 相似文献
16.
From a study of (p,t) reactions on 31P and 30Si it is suggested that in 29P the states with and , the pair , , and the pair , are related by weak coupling of a s proton with the states 01+, 02+, 21+ and 41+ respectively of 28Si. Completely atypical L = 2 angular distributions have been obtained for the and states in 29P and it is suggested that this is due to contribution by two-step processes. 相似文献
17.
18.
The two emission lines, Kα1α3h and Kα2α3h resulting from the two-electron transitions and were resolved for elemental nickel. Their measured energies agree well with calculations. Their relative intensity and their intensity relative to that of the Kα diagram lines is about 10?4. This is some 104 times larger than both theoretical results and the results of ion-atom collision experiments. 相似文献
19.
Marek Danielewski Jaeosław Da̧bek Stanisł;aw Mrowec Grażyna Siemińska 《Solid State Ionics》1985,17(4):331-335
Using the re-equilibration kinetic method the chemical diffusion coefficient in nonstoichiometric chromium sesquisulfide, Cr2+yS3, has been determined as a function of temperature (1073–1373 K) and sulphur vapour pressure (10?104 Pa). It has been found that this coefficient is independent of sulphur pressure and can be described by the following empirical equation: . It has been shown that the mobility of the point defects inCr2+yS3 is independent of their concentration and that the self-diffusion coefficient of chromium in this sulfide has the following function of temperature and sulphur pressure: . (cm2s?1). 相似文献
20.
R. Gatto 《Physics letters. [Part B]》1974,51(4):371-375
If the hadronic contribution to vacuum polarization, which is proportional to the ration of e+e? annihilation into hadrons to that into μ+μ? rises asymptotically as a power of the squared four-momentum, the ratio point is bound to be less than and this limit is approached sooner for higher β. Other models of vacuum polarizations are also considered together with their possible origin and implications. 相似文献