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1.
The temperature dependence of the field emission flicker noise spectral density functions has been investigated for potassium adsorbed on tungsten (112) planes by a probe hole technique. By integration of the spectral density functions the noise power for different frequency intervals Δ? is obtained. From the exponential temperature dependence of noise power “activation energies” qΔ? are determined. Plots of these energies versus coverage show a similar “oscillating” behaviour as recently found for or which indicates phase transitions of the adsorbed potassium submonolayers. The noise activation energies are discussed in terms of existing models and a comparison is made between the experimental q values and surface diffusion energies Ed as determined by conventional methods. 相似文献
2.
F.W. Büsser L. Camilleri L. Di Lella G.B. Pope A.M. Smith B.J. Blumenfeld S.N. White A.F. Rothenberg S.L. Segler M.J. Tannenbaum M. Banner J.B. Chèze H. Kasha J.P. Pansart G. Smadja J. Teiger H. Zaccone A. Zylberstejn 《Physics letters. [Part B]》1976,61(3):309-312
Transverse momentum distributions of , and Ko, produced in pp collisions at x = 0, have obtained at the CERN ISR. The Ko yield is in agreement with published K+, K? results, obtained at this centre-of-mass energy (√s≈44 GeV). The results on production obtained in this experiment are compared with results obtained at lower centre-of-mass energies. 相似文献
3.
J. Marro 《Physics letters. A》1976,59(3):180-182
From series expansions estimates of Sykes et al. it is concluded that the ratio for the critical amplitudes corresponding to the critical exponents β, γ and δ, respectively, behaves like a universal quantity, within reasonable bounds, for the site and bond percolation problem. 相似文献
4.
From the angular distributions of γ-rays emitted by oriented 129gTe and 129mTe nuclei implanted in iron by isotope separator, unique spin assignments could be made for the excited states of 129I at 487.4 keV , 696.0 keV , 729.6 keV , 768.9 keV , 1050.4 keV and 1111.8 keV . In addition, E2/M1 amplitude ratios for the following 129I γ-rays (energies are in keV) are derived: δ(459.6) = ?(0.076+0.037?0.148); δ(487.4) = 0.50+0.17?0.10 or δ? = 0.35+0.15?0.09; δ(556.7) = 0.06±0.02 or δ? = ?(0.10±0.02); δ(624.4) = 0.10±0.26 or δ? > 0.4; the 696.0 keV γ-ray is pure E2; δ(729.6) = ?(0.34±0.06) or δ?1 = 0.55±0.05; δ(741.1) = ?(0.27±0.10) or δ?1 = ?(0.43±0.12); δ(817.2) = 0.46±0.04 or δ?1 =0.20±0.03 if ; δ(1022.6) = ?(0.02 ±0.02) or δ?1 = ?(0.23±0.02); ; δ(1111.8) = 0.06±0.05 or δ?1 = ?(0.08±0.05). The anisotropy of the 531.8 keV γ-ray excludes as a possible spin assignment for the 559.6 keV level, so that no level is fed in the decay from 129Te. Anisotropies for the 209, 250.7, 278.4 and 281.1 keV γ-rays are also measured. Comparison of the level scheme is made with theoretical predictions from both the pairing-plus-quadrupole model and the intermediate coupling unified model. 相似文献
5.
From the scaling law for the s-channel partial wave amplitudes, which guarantees simultaneously t-channel unitarity at threshold t = 4μ2 and s-channel unitarity, we derive: (i) The intercept α(0) of the Pomeron is always one, if α(4μ2) > 1. (ii) The total and the elastic cross sections are bounded from below for s → ∞. where α(4μ2) and δ(4μ2) are the position and the type of te Pomeron singularity (J ? α(4μ2))?1?δ(4μ2) at t = 4μ2. (iii) The type of the Pomeron singularity δ(4μ2) is restricted: either or . 相似文献
6.
R. Oppermann 《Solid State Communications》1982,44(8):1297-1299
An n-orbital model describing both elastic impurity scattering and exchange interaction is examined near its instability for itinerant ferromagnetism. At the critical point and at zero temperature, long range spin fluctuations cause anomalous enhancements of the density of states near the Fermi energy with in three-dimensions (3D) and with ln2|E ? EF| in 2D. An estimation of the conductivity in a continuum analog model reveals Ω -and ln2-corrections in 3D and 2D respectively. 相似文献
7.
C.R. Leavens 《Solid State Communications》1975,17(12):1499-1504
It is rigorously shown that the superconducting transition temperature of any material for which the Eliashberg theory is valid must satisfy kBTc ? 0.2309 A, where A is the area under its electron-phonon spectral function α2F(ω). This relation is a least upper bound, not just an upper bound, in the sense that there is an optimal situation in which the equality holds. This occurs when the Coulomb pseudopotential parameter is zero and the spectral function is the Einstein spectrum Aδ(ω ? 1.750 A). These results are generalized in an approximate, but sufficiently accurate, way to the case to obtain the more useful least upper bound and the corresponding optimal spectrum . Numerical results for the functions and d(μ1) are presented for . It is shown that the Tc's of many materials (including Nb3Sn), for which experimental values of A and are available, do not lie very far below the upper bound. 相似文献
8.
Diffusion of 54Mn in Mn1?δO single crystals has been measured by a serial sectioning technique as a function of temperature (1000–1500°C) and deviation from stoichiometry (0.00003 < δ < 0.12). The value of m in the expression varies from about 6 at low Po2 at all temperatures to a value approacing 2 at high Po2 and high temperatures, thus suggesting that diffusion occurs by doubly charged vacancies at low Po2 with increasing contributions from singly charged and neutral vacancies as Po2 (and vacancy concentration) increases. For δ near 0.1, the values of D fall below the values extrapolated from smaller defect concentrations. The isotope effect for cation self-diffusion was measured by simultaneous diffusion of 52Mn and 54Mn in Mn1?δO (0.0004 < δ < 0.116) at 1300 and 1500°C. The measured values of fΔK are independent of temperature within experimental error, and decrease from a value of 0.70 at low defect concentrations to 0.37 for large values of δ. The isotope-effect results suggest that diffusion occurs by single non-interacting vacancies at low defect concentrations; defect-defect interactions become important for δ ? 0.01. The defect-defect interactions may involve essentially individual defects or may result in defect clusters; the similarity between the present isotope-effect results and those for Fe1?δ0 suggests that defect clustering plays a significant role in mass transport in Mn1?δO at large values of δ. 相似文献
9.
We have obtained a least upper bound, , on the critical temperature Tc of an isotropic superconductor with paramagnetic impurities described by the scattering matrix t for fixed values of μ1. We have also obtained the corresponding optimal spectrum . The numerical results for the functions are presented for and 0.16 in the form of universal curves representing as functions of the reduced impurity concentration . We have also established an upper limit to the reduced critical concentration for an arbitrary shape of α2F(ω)1. 相似文献
10.
G. Tarrago M. Dang-Nhu G. Poussigue G. Guelachvili C. Amiot 《Journal of Molecular Spectroscopy》1975,57(2):246-263
High resolution spectra of the ν3 band of methane, 12CH4, were recorded by using a “third generation vacuum Fourier interferometer”; a large pressure range (from 0.009 to 10 Torr) with a sample path fixed at eight meters was used, enabling observation of transitions with intensity ratios as low as . More than 350 forbidden transitions of the ν3 band, including about 125 transitions of the Q+ branch, were unambiguously identified. Of the 277 transitions retained for computations, one-hundred have 11 ≤ J ≤ 16. From combination difference relations using pairs of transitions having the same upper state energy level (forbidden-allowed and forbidden-forbidden pairs were used), 276 independent differences between ground state energy levels could be determined with uncertainties of about 0.001 cm?1.These data yielded the following values for the ground state structure constants of 12CH4 along with their standard deviations (in cm?1): , , , , , , Thus, for the first time, the scalar constant π0 has been evaluated and ir values have been obtained for the two tetrahedral constants ?0 and ξ0; furthermore, these values are in very good agreement with the ones recently determined from radiofrequency data, i.e., in cm?1: , , From these values, the 276 differences can be reproduced with an overall rms deviation equal to 0.0009 cm?1.Finally, the ground state energies of 12CH4 have been calculated for J ≤ 16. 相似文献
11.
The fluctuation of valence in some rare-earth (RE) compounds is described in terms of the effective potential seen by the RE ion. The nearly degenerate and levels of the RE ion split in energy in the presence of a repulsive potential. The energy separation (ΔE) between these levels is a function of external variables such as temperature, pressure or composition, which change the effective potential seen by the ion. The variation of ΔE with temperature is obtained for four Europium compounds from 151Eu Mössbauer isomer shift data. The temperature dependence of susceptibility is then obtained from the same (ΔE) variation and compared with experimental results. A characteristic temperature (Tυ) is found below and above which (ΔE) behave as ΔE = αT and ΔE = βT+γ respectively. 相似文献
12.
《Nuclear Physics B》1998,525(3):738-753
13.
M. Djebara M. Asghar J.P. Bocquet R. Brissot M. Maurel H. Nifenecker CH. Ristori 《Nuclear Physics A》1984,425(1):120-140
A gas ΔE ? ER telescope has been used to measure charge yields and their correlations with kinetic energies for 229Th and 232U. Even-charge yields are enhanced compared with odd-charge yields for both fissioning systems; this enhancement increases for events with higher kinetic energy. The mean odd-even effect ; it is . The energy-integrated δp and δp for different energy windows, vary strongly as a function of charge (Z) due to the underlying shells. The δp averaged over Z increases fast with kinetic energy, contrary to the existing results for 233U and 235U, where δp flattens off at low energies. For both systems, the most probable kinetic energy ē shows a strong odd-even stagger; the mean odd-even effect on energy, the latter is about twice the value for . These results are discussed in terms of the existing models. 相似文献
14.
C. Cochet C. Lewin R. Barloutaud D. Denegri A. Givernaud M.L. Turluer U. Gensch U. Kriegel H. Vogt H. Kirk D.R.O. Morrison H. Saarikko F.A. Triantis Yu. Arestov E.P. Kistenev E.A. Kozlovsky A.M. Moïseev F. Mandl 《Nuclear Physics B》1979,155(2):333-356
Inclusive production of vector and tensor mesons is studied in a K?p experiment at 32 GeV/c in the MIRABELLE bubble chamber. The , ?0 and ω cross sections are comparable, about 4 mb each. The and cross sections are also comparable, about 1 mb each. The (890), Φ, (1420) and f cross sections beam fragmentation; ? production is almost forward-backward symmetric in the c.m.s. The pT production slopes of and ? are similar, the Φ slope is shallower. Vector and tensor mesons alone are responsible for ?50% (?60%) of final-state pions 相似文献
15.
An energy-independent multipole analysis of pion photoproduction in the first resonance region has been performed in which special care has been taken in the selection and normalization of the data. The results obtained are a significant improvement on those of earlier analyses. Three features are of particular interest: a zero in the multipole at resonance; a smooth multipole showing the onset of the P11(1470) resonance; and evidence for the position of the Δ+ resonance being different from those of the Δ++ and Δo resonances. A comparison is made with the recent energy-dependent analyses, indicating agreement in the gross features of the multipoles but showing significant differences in essential details. 相似文献
16.
The half-lives of the states at 522.6 and 393.9 keV in 113Cd and 115Cd have been determined to be 0.322±0.012 and 0.75± 0.03 ns, respectively. Values of the ) and the energy difference in odd Cd (A = 113–119) are compared with those in neighbouring even Cd. The level properties are interpreted in the framework of the triaxial rotor model. 相似文献
17.
y.И. caфpoнoвa 《Journal of Quantitative Spectroscopy & Radiative Transfer》1975,15(3):231-242
Energies and dipole matrix elements have been calculated for He, Li, Be, B, C, N, O, F, and Ne-like ions (configurations 1s22sn12pn2?1s22sn1?12pn2+1). The Hartree-Fock energy, the correlation energy, and relativistic corrections were taken into account. Relativistic corrections were obtained by computing the entire quantity HB. Numerical results are presented for energies of the terms in the form , and for the fine structure of the terms in the form . Dipole matrix elements are required for calculation of oscillator strengths or transition probabilities. For the dipole matrix elements, two terms of the expansion in have been obtained. Numerical results are presented in the form P(a, a′) = (a/Z)[1 + (τ/Z)]. 相似文献
18.
Several distinct features have been observed in the photoluminescence spectrum of heavily Zn-doped GaAs, in the range between 1.65eV to 2.25eV. They are attributed to direct recombination across the Eo+?o gap and to indirect processes related to Xc1 and Xc3. The Xc1 minima are thus located to be 1.935±0.01eV above the top of the valence band at 100K. Their shear deformation potential X2 is found to be . 相似文献
19.
The cross section for production of single photons in the process is calculated including selectron propagator and photino mass effects and is found to be significantly smaller than the local limit for selectron masses ? 35 GeV/c2. Numerical results for the cross section are obtained as a function of selectron masses for photino masses and electron beam energies E = 14.5, 25, and 35 GeV appropriate to PEP, PETRA, and TRISTAN, respectively. 相似文献
20.
H. Van Cong S. Brunet S. Charar J.L. Birman M. Averous 《Solid State Communications》1983,45(7):611-614
The band-gap narrowing ΔEg, opt and ΔEg, elec (or ΔEg, eff) for optical and electrical energy gaps of the n-type impure silicon at 300 K, are investigated based on simplified models of heavily doped semiconductors. It is suggested that, for is significantly larger than ΔEg, opt, in good agreement with observed results. This difference is caused especially by the effect of the polaron. 相似文献