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61.
R.E.L. Green D.H. Boal R.L. Helmer K.P. Jackson R.G. Korteling 《Nuclear Physics A》1983,405(3):463-496
A 9Be(p, 2p) coincidence experiment performed to further elucidate the reaction mechanism for the production of energetic wide-angle protons in intermediate-energy proton-induced reac- tions is reported. Detectors in a coplanar geometry were used to measure coincidences between trigger protons at 90° to the beam and forward-angle protons on the opposite side of the beam. The incident proton energy was 300 MeV. We report both the inclusive spectra for the trigger protons and the differential mean multiplicities for the coincidence events.The outgoing proton energies were measured using NaI detectors. Trigger protons were grouped into 10 MeV bins covering the kinetic energy range from 55 to 155 MeV. The forward protons were measured over a kinetic energy range of 65–280 MeV and an angular range of 14–60° with respect to the beam.The present results are compared with two previous experiments which covered a more restrictive kinematical range. Calculations are performed with both phase-space and direct knockout models, and compared with experiment. Observation of angle and energy correlation effects suggested by knockout models indicate that such direct mechanisms provide a significant contribution to energetic wide-angle inclusive proton spectra. 相似文献
62.
63.
The decay of 134Ce to doubly odd 134La has been studied using Ge(Li) and Si(Li) photon detectors. Samples of the 134Ce(75.9 h)- 134La(6.67 min) have been produced by ≈ 800 MeV proton bombardment of Pr foils in LAMPF, followed by chemical and mass separation. To increase the sensitivity (by up to a factor ≈ 50) for detection of 134Ce γ-rays in the presence of the interfering 134La activity, the 134Ce-134La samples were loaded onto a HDEHP column and the 134La eluted off continuously. Gamma-ray singles and γ-γ coincidence measurements were made using the 134Ce activity remaining on the column as the source. Some 32 γ-rays, ranging in energy up to 355 keV, are observed to be associated with this decay. Approximately 30 of these have been fitted into a level scheme for 134La with excited states at energies of 31, 54, 93, 136 or 148, 162, 187, 150 or 205, 252, 294 and 355 keV. Only limits can be set for the spin and parity values of each of these states. The observation of γ-rays with energies up to 355 keV indicates that the previously reported values of ≈ 0.1 MeV for the 134Ce electron-capture decay energy, inferred from the K-electron capture probability, are incorrect. 相似文献
64.
65.
Helmer Fjellvåg Arne Kjekshus Andrzej Ziȩba Simon Foner 《Journal of Physics and Chemistry of Solids》1984,45(7):709-718
The magnetic properties of polycrystalline samples of Mn1?tTtP (T = V, Cr, Fe and Co for 0.00 ≦ t ≦ 0.50) are studied by magnetic susceptibility, magnetization and neutron diffraction measurements. The magnetic phase diagrams of the Mn1?tTtP phases exhibit paramagnetic, ferromagnetic, helimagnetic and spin glass regions depending on temperature and substitution (T, t). The concentrated spin glass regions observed in Mn1?tVtP and Mn1?tCotP (0.30 ≦ t ≦ 0.50) are believed to result from the disorder in the metal sublattice. The variation of the magnetic moment of the ordered Mn1?tTtP phases with the substitution (T, t) is discussed. 相似文献
66.
67.
John C. Helmer 《Analytica chimica acta》1980,122(1):27-40
An analytic function operating on experimental data is optimized for making the most accurate measurement of a parameter of the expected data, under the conditions of non-stationary shot noise. The value of the parameter is obtained by equating the operation on experimental data with the same operation on the expected data which contains the parameter as an unknown value. If the operation is represented by a weighting function, the form of the optimum weighting function depends on the initial transformation of the experimental data by the measuring instrument. The optimum weighting function always contains the derivative of the expected signal with respect to the unknown parameter, divided by the time-dependent variance of the received signal. Weighting functions for the logarithmic output of a spectrophotometer are described. The superiority over least-squares curve-matching is shown. A method for determination of peak position by optimum slope measurement is derived. In general, the optimum weighting function is not a matched filter. The optimum result is the same for center-of-gravity measurements. The optimum parameter measurement is equivalent to a least-squares error minimization weighted by the inverse variance or mean-square noise level. This variance weighting is significant in photometric measurements limited by shot noise or other measurements described by Poisson statistics, such that the mean-square noise level varies with time. The form of the optimum filter, for non-white, non-stationary noise is derived. 相似文献
68.
I. Ursu R. Alexandrescu V. Drăgănescu C. Grigoriu I. N. Mihăilescu I. Morjan A. M. Prokhorov N. V. Karlov A. S. Lagutchev A. N. Orlov Yu. N. Petrov 《Applied physics. B, Lasers and optics》1988,47(1):61-65
New experimental results are reported pointing to the possibility of a laser control of the resonant gases transit through capillaries in the Knudsen and intermediate regimes. 相似文献
69.
The absorption and photoluminescent spectra of nitrogen doped GaAs1?χPχ epitaxial layers were studied in the alloy composition range 0.58 ? χ ? 0.77. The structure in the absorption and luminescent spectra are analysed. 相似文献
70.