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1.
It is demonstrated that in a full nonlocal pseudopotential calculation of the density of states, the results from the standard formula, , do not differ significantly from those using the Green-function method and are reliable for simple liquid metals, despite the fact that there is an uncertainty in treating Ek as a dispersion function. 相似文献
2.
The X-ray structure (293 K) of UO2(H2PO4)2·3H2O has been refined (R = 0.062): Mr = 518g, space group: P21/c (Z = 4); , , , β = 105.65(1)°, ; Dc = 3.17 Mg m?3. The structure consists of infinite chains along the (101) axis with U atoms bridged by two H2PO4 groups. The U atom is surrounded by a pentagonal bipyramid of oxygen atoms, one of them being an equatorial water molecule. The cohesion between the chains is ensured by hydrogen bonds involving the two last water molecules. An assignment of IR and Raman bands with isotopic substitution spectra is proposed. A phase transition at 128 K was made evident by DSC and spectroscopy. The room-temperature phase is characterized by a high disorder of the OH bond orientation while in the low-temperature phase H2O and POH species appear well oriented. The conductivity seems to occur by proton transfer and protonic-species rotation at the POH-water molecular interface between the chains. ac conductivity has been determined by means of the complex-impedance method (; E ~ 0.20 eV). 相似文献
3.
The 0-0, 1-1, 2-2, and 3-3 bands of the A2Π-X2Σ+ transition of the tritiated beryllium monohydride molecule have been observed at 5000 Å in emission using a beryllium hollow-cathode discharge in a He + T2 mixture. The rotational analysis of these bands yields the following principal molecular constants. From the pure electronic energy difference (EΠ - EΣ)BeT = 20 037.91 ± 1.5 cm?1 and the corresponding previously known values for BeH and BeD, the following electronic isotope shifts are derived and related to the theoretical approach given by Bunker to the problem of the breakdown of the Born-Oppenheimer approximation. 相似文献
4.
A weak emission spectrum of I2 near 2770 Å is reanalyzed and found to to minate on the A(1u3Π) state. The assigned bands span v″ levels 5–19 and v′ levels 0–8. The new assignment is corroborated by isotope shifts, band profile simulations, and Franck-Condon calculations. The excited state is an ion-pair state, probably the 1g state which tends toward . In combination with other results for the A state, the analysis yields the following spectroscopic constants: T″e = 10 907 cm?1, ″e = 1640 cm?1, ω″e = 95 cm?1, ; T′e = 47 559.1 cm?1, ω′e = 106.60 cm?1, . 相似文献
5.
The energies and the entropies of the spin-glass state and the paramagnetic state at T = 0 of the random-bond Ising mixture of the ferromagnetic bond (concentration p) and the antiferromagnetic bond (concentration 1 ? p) on the square lattice are calculated by the method of the square approximation in the simple version. A self-consistent relation that the partial trace of the normalized density matrix of the square cluster is equal to that of the vertex () leads to an integral equation for the distribution function of the effective fields, and it is solved exactly at T = 0. The symmetric solution of the integral equation contains the paramagnetic state and two spin-glass states, SG1 and SG2. The energies and the entropies of these states are obtained as functions of the concentration p. The values of the energies per spin at are -0.75|EF|, -0.72746|EF|, -0.72543|EF|, and correspond to a minimum, a saddle point, and a maximum, respectively, and the values of the entropies are 0, 0.082886kB, and 0.054457kB, respectively. The present results are compared with those of the pair approximation and discussed. 相似文献
6.
The Raman active fundamentals ν1(A1g), ν2(Eg), ν5(F2g), and the overtone 2ν6 of SF6 have been investigated with a higher resolution and the band origins were estimated to be: ν1 = 774.53 cm?1, ν2 = 643.35 cm?1, ν5 = 523.5 cm?1, and 2ν6 = 693.8 cm?1. Raman and infrared data have been combined for estimation of several anharmonicity constants. The ν6 fundamental frequency is calculated as 347.0 cm?1. From the analysis of the ν2 Raman band, the following rotational constants of both the ground and upper states have been calculated: ; . 相似文献
7.
The dispersion of the plasmon and its resonance-like penetration into the single particle excitation band has been measured by electron spectroscopy of polycrystalline Al up to wave number . For there are deviations from the RPA dispersion in the free electron gas due to band effects. Within the experimental accuracy, there is zero dispersion at . This levelling off may be qualitatively explained by electron short range correlations. 相似文献
8.
J.C.D. Brand U.D. Deshpande A.R. Hoy S.M. Jaywant 《Journal of Molecular Spectroscopy》1983,100(1):143-150
The E-B (0g+-0u+) band system of Br2 has been investigated at Doppler-limited resolution using polarization labeling spectroscopy. Merged E state data for the three naturally occurring isotopes in the range vE = 0–16, expressed in terms of the constants for 79Br2, are (in cm?1) Y0,0 = 49 777.962(54), Y1,0 = 150.834(22), Y2,0 = ?0.4182(28), Y3,0 = 6.6(11) × 10?4, Y0,1 = 4.1876(28) × 10?2, Y1,1 = ?1.607(16) × 10?4, and Y0,2 = 1.39(39) × 10?8. The bond distance is , and the diabatic dissociation energy to . 相似文献
9.
We provide a simple proof that the kth gap, Δk, for the Mathieu operator is , a result obtained (up to the value of an integral) by Harrell. The key observation is that what is involved is tunneling in momentum space. 相似文献
10.
In this paper we consider a product of n complex m×m matrices Ak (k=1,…,n) with singular values ∝(k)i ordered in decreasing magnitude. Using the spectral resolution for the operators , it is shown that This inequality is an extension of an inequality of von Neumann in the simple case that n=2. The necessary and sufficient condition for the equality sign to hold is established. Application of Hölder's inequality leads to further inequalities which can be useful in statistical mechanics. 相似文献
11.
Aluminum oxide layer dissolution was studied between 700 and 1200 K in the substrate areas of W〈111〉, Mo〈111〉, and on W{110} by means of FEM. Varying the electric field strength, F, between +45 and , two types of dissolution could be observed: dissolution by surface diffusion (low F's) and dissolution by ion desorption (high F's). It is assumed that aluminum suboxides — preferentially AlO — are involved in the dissolution processes. The preexponential factors, AF, of an Arrhenius-Frenkel type equation were measured as a function of F. The field dependence of AF is determined by the dissolution mechanism: (a) dissolution by diffusion: (μ molecular dipole moment, 1T ≡ isokinetic for W〈111〉, log A00 = ? 6.0 and ; for Mo〈111〉, log A00 = ? 3.1 and ; and (b) dissolution by ion desorption: ; for A+0 = ? 22 and ; for W〈111〉, log A+0 = ? 21 and . Using earlier proposed safeguards, isokinetic relationships (compensation effects) could be established for each of the two dissolution processes. The coordinates of the isokinetic points have the following average values: and for diffusion; and for ion desorption. The entropy changes (at , zero field strength, and unit pressure) for the phase changes: solid layer → diffusion layer and solid layer → ion gas, are of the order of · mol and · mol, respectively. The two dissolution mechanisms can be described by the following Arrhenius-Frenkel type equations: for diffusion and for ion desorption. 相似文献
12.
Simple approximative equations governing the temporal behaviour of both the mean photon number, , and its mean square deviation, Δn2, in the process of k-photon absorption (k = 1, 2, …) are derived and solved for initial photon distributions characterized by ? 1 and Δn2 ? -2. It is readily shown that such an initial distribution, in the course of attenuation, tends to a distribution for which . Hence, for k > 1, the distribution is narrower than a Poisson distribution which means that photon antibunching occurs. The feasibility of a Hanbury Brown and Twiss type experiment allowing to detect this effect utilizing two-photon absorption is discussed, and an estimation of the required order of magnitude of the two-photon absorption cross-section is presented. 相似文献
13.
The static structure factor S(k) of liquid indium has been measured accurately down to using CuKα radiation with reflection geometry. The direct pair correlation function in k space is analyzed to demonstrate the utility of this technique in reducing errors in the resulting direct pair correlation function in configuration space. 相似文献
14.
Takehiko Tanaka Robert W. Field David O. Harris 《Journal of Molecular Spectroscopy》1975,56(2):188-199
A rotational assignment of approximately 80 lines with Ka′ = 0, 1, 2, 3, and 4 has been made of the 593 nm band of NO2 using cw dye laser excitation and microwave optical double-resonance spectroscopy. Rotational constants for the 2B2 state were obtained as A = 8.52 cm?1, B = 0.458 cm?1, and C = 0.388 cm?1. Spin splittings for the Ka′ = 0 excited state levels fit a simple symmetric top formula and give . Spin splittings for Ka′ = 1 (N′ even) are irregular and are shown to change sign between N′ = 6 and 8. Assuming that the large inertial defect of 4.66 amu Å2 arises solely from A, a structure for the 2B2 state is obtained which gives and an ONO angle of 105°. Alternatively, weighting the three rotational constants equally gives and θ = 118°. 相似文献
15.
Laser-induced fluorescence excitation has been used to measure Stark splittings of selected lines in the and band systems of H2CS in electric fields up to 13 kV/cm. The derived excited state a-axis dipole moments are 0.820 ± 0.007 D for the 41 level of the 1A2 state; 0.838 ± 0.008 D for the zeroth vibrational level of 1A2; and 0.534 ± 0.015 D for the zeroth vibrational level of the 3A2 state. These results are compared with the corresponding values of H2CO, and interpreted in terms of the changing localization of the π and orbitals accompanying electronic excitation. 相似文献
16.
The rotational motion of the OH? ion was studied in cubic NaOH at 575 K with quasielastic incoherent neutron scattering. The data are compared to two simple models yielding values for the radius of rotation R, the translational mean square displacement 〈u2〉H, the rotational jump rate τ?1 and the rotational diffusion coefficient DR. The following parameter values are obtained: (a) rotational jump model: , , (b) rotational diffusion model: . 相似文献
17.
Toshio Suzuki 《Nuclear Physics A》1982,379(1):110-124
The mean energy of the giant Gamow-Teller resonance state (GTS) is studied, which is defined by the non-energy-weighted and the linearly energy-weighted sum of the strengths for ΣAi = 1τi?σi? Using Bohr and Mottelson's hamiltonian with the ξl· σ force, the difference between the mean energies of GTS and the isobaric analog state (IAS) is expressed as. The observed energy systematics is well explained by kτ?kστ≈ 4/A MeV. The relationship between the mean energies and the excitation energies of the collective states in the random phase approximation for charge-exchange excitations is discussed in a simple model. From the excitation energy systematics of GTS, the values of kστ and the Migdal parameter g′ are estimated to be about , respectively. 相似文献
18.
Moshe Moshe 《Physics letters. [Part B]》1981,98(4):297-300
Though high twist terms are becoming important as x→1, or equivalently, in large n moments, their detection in this regime in deep inelastic lepton scattering needs special caution. The high order terms in the twist two component are strongly dependent on n; one finds that at the perturbative expansion is invalid whereas higher twist terms are important at . Since grows very fast with n the necessary requirement for any deep inelastic phenomenological analysis, namely , cannot hold for too large moments. The scheme dependence of ak, αk and bk is also discussed. 相似文献
19.
D.C. Look 《Journal of Physics and Chemistry of Solids》1975,36(12):1311-1315
Hall-effect and magnetoresistance measurements have been carried out in GaAs : Cr as functions of magnetic field strength (B = 0–18kG) and temperature (T = 125–420°K). Independent solutions for the mobilities, μn and μp, and the carrier concentrations, n and p, are obtained from the basic mixed-conductivity equations. These quantities, as well as the intrinsic carrier concentration, ni are then calculated as a function of temperature for one sample, and subsequent analysis yields the following values in the range T = 360–420°K: an acceptor (presumably Cr) energy EA = 0.69±0.02eV (from the valence band); the bandgap energy Eg = Eg0 + αT, with Ego = 1.48±0.02eV, ; , decreasing slightly with temperature; = 350± 50 ; and an acceptor-to-donor concentration ratio, itNA/ND?8. The electron mobility appears to be limited by neutral impurity scattering, with NA ? 2 × 1016cm?3. Several other samples were also investigated but as a function of temperature only (at B = 0). At room temperature both positive (p-type) and negative (n-type) Hall coefficients were observed. 相似文献
20.
The recent increase of experimental data concerning the giant monopole resonance energy EM gives information on the incompressibility modulus of nuclear matter, provided one can extrapolate the incompressibility of a nucleus KA, defined by , to the infinite medium. We discuss the theoretical interpretation of the coefficients of an expansion of KA by studying the asymptotic behaviour of two RPA sum rules (corresponding to the scaling and the constrained model), evaluated using self-consistent Thomas-Fermi calculations. We show that the scaling model is the most suitable one as it leads to a rapidly converging expansion of the corresponding incompressibility KAs, whereas this is not the case with the constrained model. Some semi-empirical relations between the coefficients of the expansion of KAs are established, which reduce to one the number of free parameters in a best-fit analysis of the experimental data. This reduction is essential due to the still limited number and accuracy of experimental data. We then show the compatibility of the data given by the various experimental groups with this parametrization and obtain a value of Kn.m. = 220 ± 20 MeV, in good agreement with more microscopic analyses. 相似文献