共查询到20条相似文献,搜索用时 31 毫秒
1.
C.N. Waddell E.M. Diener R.G. Allas L.A. Beach R.O. Bondelid E.L. Petersen A.G. Pieper R.B. Theus C.C. Chang N.S. Chant 《Nuclear Physics A》1977,281(3):418-442
The (p, pn) reaction on 2H, 6Li, 7Li, 9Be has been studied at 47 MeV bombarding energy. Excitation energy spectra and energy sharing spectra are presented. Fragmentary information on 10B, 11B and 12C was also obtained. Sequential decay contributions to the 6Li(p, pn)5Li1 reaction suggest an admixture of parentage for the (3?), 23 MeV excited state of 6Be. A possible 15.5 MeV excited state in 6Be is reported. An extensive study of the 9Be (p, pn)8Be reaction for 45 MeV protons was made. Results for θp = θn = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θn = 40°, θp = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θp/θn = 40°/45°, 38.5° are reported and compared to DWIA calculations. Agreement is good when the lower momentum components of the wave function are sampled, and deteriorates as higher momenta are required. Results are in agreement with the Cohen and Kurath spectroscopic factors for 9Be. 相似文献
2.
G.C. Salzman Gerald G. Ohlsen J.C. Martin J.J. Jarmer T.R. Donoghue 《Nuclear Physics A》1974,222(3):512-524
Angular distributions of six polarization transfer coefficients ; of the four analyzing powers Ay(θ), Axx(θ), Ayy(θ), and Azz(θ); and of the polarization function Pý(θ), have been measured atEd = 10.00 MeV for the reaction 2H(d, n)3He. Measurements were made for neutron lab angles between 0° and 80° in 10° steps. Additionally the y-axis associated quantities were measured at θ1ab = 99°. Most of the measured coefficients are large at some angles and all show considerable variation with angle. 相似文献
3.
The flash decomposition of DCOOH was studied on a clean nickel (110) surface following adsorption at 37°C. The reaction proceeded by a two-dimensional autocatalytic mechanism to form D2, CO2 and CO products. The results indicated DCOOH adsorbed dissociatively at 37°C by splitting off H2O and forming an adsorbed molecule composed of DCO and DCOO. Above ten percent of saturation coverage these molecules formed a condensed phase or island structure. The decomposition of the molecules was rate determining for the formation of CO2 and D2 products. Theoretical calculations for branched chain mechanisms and coadsorption experiments with CO and H2 separately with DCOOH indicated the intermediate involved in the explosion was not associated with the observed product molecules. The intermediate in the explosive decomposition was shown by interrupted flashes to be stable at 37°C. The autocatalytic flash decomposition curves were explained by reaction occurring at bare metal sites within the islands, and as product molecules desorbed the number of sites increased, causing the rate to accelerate. The rate of decomposition was well described by the , where c is the surface concentration, cI is the initial surface concentration, and f is the density of initiation sites. The activation energy of 26.6kcal/mol was determined from heating rate variation. The narrow flash curves were fit with a first order pre-exponential factor of 1.6 × 1015 sec?1 with a density of initiation sites of 0.004. 相似文献
4.
The reaction 12C(7Li, t)16O has been studied at with the LASL tandem accelerator and QDDD magnetic spectrometer. Angular distributions to levels with Ex < 11 MeV have been obtained from 0° to 90°, including 0°. The results have been analyzed with finite-range distorted-wave Born approximation theory. The α-particle spectroscopic factors and reduced widths obtained are compared with those calculated with group theory (SU(3)) and other models. The analysis of data for the 7.1 and 9.6 MeV Jπ = 1? levels, which are of great importance in stellar helium buring, yields a ratio, R, of dimensionless reduced α-widths . The observed line width of the 9.6 MeV level (Γc.m. = 390 ± 60 keV) is less than the accepted value (Γc.m. = 510 ± 60 keV) and implies θ2a(9.6 MeV) ≈ 0.6. These results as well as data for the 6.92 MeV Jπ = 2+ and 10.35 MeV Jπ = 4+ “α-cluster” states indicate 0.09 < θ2a(7.1 MeV) < 0.33 with a mean value θ2a(7.1 MeV) = 0.14 ± 0.04. The implication for stellar helium burning is discussed. 相似文献
5.
Alkali atoms were scattered with hyperthermal energies from a clean and an oxygen covered (θ ≈ 0.5 ML) W(110) surface. The trapping probability of K and Na atoms on oxygen covered W(110) has been measured as a function of incoming energy (0–30 eV) and incident angle. A considerable enhancement of trapping on the oxygen covered surface compared to a clean surface was observed. At energies above 25 eV there are still K and Na atoms being trapped by the oxygen covered surface. From the temperature dependence of the mean residence time τ of the initially trapped atoms the pre-exponential factor τ0 and the desorption energy Q were derived using the relation: . On clean W(110) we obtained for Li: , Q = (2.78 ± 0.09) eV; for Na: τ0 = (9 ± 3) × 10?14 sec, Q = (2.55 ± 0.04) eV; and for K: τ0 = (4 ± 1) × 10?13 sec, Q = (2.05 ± 0.02) eV. Oxygen covered W(110) gave for Na: τ0 = (7 ±3) × 10?15 sec, Q = (2.88 ± 0.05) eV; and for K: , Q = (2.48 ±0.05) eV. The adsorption on clean W(110) has the features of a supermobile two-dimentional gas; on the oxygen covered W(110) adsorbed atoms have the partition function of a one-dimen-sional gas. The binding of the adatoms to the surface has a highly ionic character in the systems of the present experiment. An estimate is given for the screening length of the non-perfect conductor W(110):ks?1≈ 0.5 Å. 相似文献
6.
Eizi Hirota Yasuki Endo Shuji Saito Kazuhiko Yoshida Ichiro Yamaguchi Katsunosuke Machida 《Journal of Molecular Spectroscopy》1981,89(1):223-231
The pure rotational spectra of three deuterated ethylenes, CH2CD2, CH2CHD, and cis-CHDCHD, were observed by microwave spectroscopy, and the rotational and centrifugal distortion constants were determined precisely. The dipole moment of CH2CD2 was calculated from the Stark effects to be 0.0091 ± 0.0004 D. From the observed rotational constants the average structure was calculated to be , , θz(CCH) = 121.28 ± 0.10°, and , where the errors include one standard deviation in the fitting and errors due to an uncertainty (±0.03°) in θz(CCH) - θz(CCD). 相似文献
7.
We studied the energy width and the width in reciprocal space Δq of the central mode of SrTiO3 above Tc. At Tc+4° we observed an energy width of about 6×10?7 eV. If the measured Δq is interpreted by a correlation length we obtain . 相似文献
8.
W.J. Fredericks Paul R. Collins David F. Edwards 《Journal of Physics and Chemistry of Solids》1984,45(5):471-479
The Mandel'shtam-Brillouin and Gross scattering was measured for a series of purified KBr crystals. The ratio , which for a pure, perfect crystal would be the Landau-Placzek ratio, was found to vary with the type of reactive gas treatment used in the final purification. With these crystals both the longitudinal and mixed mode bands were observed with θ and φ equal to 90°. The ratio was in agreement with calculated intensity ratios and the Δμ for these bands gave C11 + C12 = 41.6 GPa and C44 = 5.18 GPa. 相似文献
9.
The analyzing power Aγ(θ) for neutron-proton scattering has been measured for θ = 90°(c.m.) from 13.5 to 16.9 MeV and from θ = 50° to 145°(c.m.) at 16.9 MeV. Extensive Monte Carlo calculations have been made to correct for multiple scattering effects. Overall uncertainties are about ± 0.002. All the Aγ(θ) data, but primarily those at 16.9 MeV, disagree with predictons based on the phase-shift sets which have been derived previously by way of global analyses of nucleon-nucleon scattering data. Data for the product σ(θ)Aγ(θ) have been fitted with an expansion of the form (sin θ)(. For the first time the need for a non-zero a2 has been illustrated for energies below 20 MeV. This parameter is shown to be related to the nucleon-nucleon F-state spin-orbit phase parameter. In addition, the P, D, and F spin-orbit phase parameter values derived from the present data differ significantly from the ones based on the Yale-IV and Liver-more-X global analyses. The derived D and F spin-orbit phase parameters also differ from those obtained in the recent analysis of nucleon-nucleon scattering data by Arndt et al. 相似文献
10.
J.J. Hauser 《Solid State Communications》1975,17(12):1577-1580
The electrical resistivity of amorphous carbon films getter-sputtered at 95°K is well fitted between 300 and 20°K by the relation with T0 ? 7 × 107K. This behavior suggests a hopping conductivity very similar to that found in other amorphous semiconductors. 相似文献
11.
The first observation of the ESR spectra of Mn2+, entering substitutionally for Fe2+ in the Van Vleck paramagnet FeS2 (polycrystals), is reported. The data from 5 to 295 K fits the spin-Hamiltonian + , with g = 2.000 ± 0.001, A/β = ?95.0 ± 0.5 Oe and D/β varying from 50 Oe (5K) to 59 Oe (295 K). The temperature dependence of D can be described in terms of a single phonon-mode with frequency ? 145 cm?1. 相似文献
12.
The electrical resistivity and Hall coefficient of Zn3P2 have been measured for single crystal and thin polycrystalline film samples which were annealed over a range of equilibrium vapor compositions and temperatures. The room temperature electrical resistivity of single crystal samples annealed at 573 K varied from approximately 105Ω-cm for single crystals heated in equilibrium with zinc to 10 Ω-cm for those annealed in a phosphorus rich ambient. Hall measurements indicate that a variation in carrier concentration is responsible for these changes. The experimentally observed dependence of carrier concentration [h° ], (cm?3) on phosphorus pressure is given by [h°] = 1.32 · 1016 [p(P4)]0.13 for samples annealed at 573 K. The experimentally determined pressure dependence is in good agreement with a model based on phosphorus interstitials acting as acceptors. The pressure and temperature dependence of the carrier concentration yield the equilibrium constant KI for the formation of interstitial phosphorus defects according to the reaction where . The accommodation of phosphorus interstitials is discussed in light of the crystal structure of Zn3P2. 相似文献
13.
He+, Ne+ and Ar+ ions with energies E1 between 50 and 1000 eV were used to bombard a polycrystalline Cu target at an angle of 45°. The energies, E2, of the Cu1+ ions sputtered at 90° to the primary beam were investigated using a UHV magnetic sector mass spectrometer. The maxima of the energy distributions as measured by the instrument, were at values of E2 of about 4 eV (±1 eV), nearly independent of e1 and primary ion mass. Plots of log N(E2) versus log E2 displayed limited linear portions over which the functional dependence of N(E2) is proportional to E2?0.5. Plots of the average secondary ion energy, ē2, versus the energy transferred by the primary ion to a Cu atom in a direct collision , indicate that ē2 increases linearly with transfer energy up to a transferred energy of about 200 eV, independent of primary ion mass. Above about 200 eV transferred energy, ē2 asymptotically approaches values which depend upon primary ion mass. At transferred energies below about 200 eV, the collision kinematics in the fust few collisions appears to dominate the emission process. 相似文献
14.
The cross section for the reaction has been measured at θlab = 135° over the proton energy range 93 ≦ Ep ≦ 418 keV. The results are in good agreement with the less precise but much earlier measurements of Schardt, Fowler and Lauritsen (1952). An analysis of the present data in terms of a two-level calculation including the 338 keV (1?) and 1028 keV (1?) resonances determines a zero-energy intercept for the astrophysical S-factor of S(0) = 78 ± 6 MeV · b. 相似文献
15.
The spontaneous magnetization of the sublattice vs temperature in the antiferromagnetic NiO was measured by the neutron diffraction method. Temperature changes of the Bragg peaks (111), (222), (333) and (444) with the wavelengths of neutrons , , and , respectively were simultaneously investigated by the neutron time-of-flight spectrometer. On the basis of these measurements, the transition temperature from the antiferromagnetic into the paramagnetic phase was determined, TN = (523 ± 1)°K. The temperature function of the (111) magnetic peak intensity has been accepted to be I ~ (TN?T)2β. According to the present measurements the critical point exponent is 0.33 ± 0.020.04. 相似文献
16.
Zhao Zhiyong 《Nuclear Physics B》1983,212(2):224-236
The phenomenological predictions of the SO(10) supersymmetric grand unified model (SO(10) SGUM) for the mass scales M1, M2, weak angle ifsin2θw, quark-leptons mass ratios , , and proton lifetime τp are estimated by using renormalization group analysis at one-loop level. In contrast with SU(5) SGUM, we find that the SO(10) SGUM still has problems with τp but not with sin2θw and , which may suggest that supersymmetry would be bro at a mass scale . 相似文献
17.
Using a method developed by Montgomery we have measured simultaneously σ| and σ⊥ the conductivities parallel and perpendicular to the c-axis respectively in single crystals of K2[Pt(CN)4]Br0·30.3(H2O). The anisotropy is of the order of 105 at room temperature but decreases to 3.103 at 35°K.None of the hitherto proposed models allows a detailed comparison between predicted and measured anisotropy. However, the experimental results seem to contradict the two dimensional variable range hopping model. The Bloch, Weisman and Varma model predicts an infinite anisotropy and thus can not be compared with experiment.Recent diffuse X-ray scattering and NMR experiments suggest that the material becomes a band semi-conductor at low temperatures due to a Peierls instability. This model is consistent with our results. While defects and random potentials do not seem to play the dominant rôle assumed in earlier models, they may determine the longitudinal mobility of the excited carriers and hence the anisotropy. 相似文献
18.
The surface self-diffusion coefficients, Ds, on a Ni(110) crystal are measured by a mass transfer technique in [10] and [001] directions in the temperature range 773–1573 K. The surface cleanliness was checked by Auger electron spectroscopy. LEED investigations showed that the sinusoidal surface profile consisted of (110) terraces and monatomic steps. The temperature dependence of Ds can be expressed by and at temperatures below 1150 K. Theoretical values for the activation energies of surface migration were calculated in the framework of the pairwise interaction model. Together with an estimate for the formation energy of adatoms of , one obtains for the activation energy of surface self-diffusion 17 and for [10] and [001] direction, respectively. At T > 1150 K the anisotropy in Ds begins to vanish. Surface diffusion in [10] direction at T < 1150 K is most likely taking place by a simple adatom hopping process. Circumstantial evidence indicates that diffusion in [001] direction does not occur by a simple hopping process but by a more complex mechanism involving higher energy surface diffusion states. This isotropic process is suggested to take place for both directions at T < 1150 K. 相似文献
19.
Two-magnon Raman scattering in the planar quadratic antiferromagnet K2FeF4 is investigated. The temperature dependence of the energy shift is in good agreement with second-order Green-function theory, as is the linewidth at low temperature. Numerical results, including renormalization, are the Heisenberg exchange and the anisotropy , but with . 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