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21.
We gather together in a unified notation formulas for electromagnetic decay rates of resonances and cross sections for electroproduction and e+e? annihilation for all those processes which can be expressed in terms of matrix elements of the electromagnetic current between single particle (or resonant) helicity states. We show in complete generality how to decompose such helicity matrix elements into form factors which are free of all kinematic singularities and constraints simultaneously at both physical thresholds, and relate them to the familiar multipole moments and to some others which have been used in data analysis. Tables are given of the form factor decomposition of the helicity matrix elements for many cases of actual and potential practical interest. 相似文献
22.
J. M. Pollard 《BIT Numerical Mathematics》1975,15(3):331-334
We describe briefly a novel factorization method involving probabilistic ideas. 相似文献
23.
D. P. E. Dickson R. K. Pollard B. Borch-Iohnsen R. J. Ward T. J. Peters 《Hyperfine Interactions》1988,42(1-4):889-892
Mössbauer spectra obtained from the haemosiderin isolated from ironoverloaded horse and reindeer spleen and liver show superparamagnetic behaviour with a much lower transition temperature than haemosiderin from iron-overloaded human spleen. These data clearly indicate the existence of different forms of haemosiderin, which are primarily distinguishable by Mössbauer spectroscopy. 相似文献
24.
25.
Mössbauer spectra of amorphous FexNi80- x Si10B10 (x=10,50) and Fe80B20 have been taken at 4.2-300K and in 0-6T applied magnetic fields. Detailed analysis shows that the standard deviation of the magnetic hyperfine field σ(B) varies with temperature depending on the iron concentration. For small x the variation is taken as evidence for a break-down of long-range magnetic order. Temperature induced changes in the fluctuations and correlations of the hyperfine parameters are reported. In all cases the isomer shift fluctuations are small compared to those of the first-order electric quadrupole splitting (u); neither are strongly temperature dependent. The correlation <ΔBΔu> is negative and increases with temperature. For Fe80B20, <ΔBΔδ> is positive and increases with temperature, whereas for Fe-Ni-Si-B it is small, negative, and temperature invariant. 相似文献
26.
An automated method for determining the iodine value for various industrial fatty acids is described. The method is based on flow-injection techniques and the chemistry is a modified version of the standard Wij's solution method. The system is fully computerized with an AIM-65 microcomputer. Two detection system, u.v.-visible absorbance and potentiometric sensing, are compared. Results comparable to the conventional method are obtained. Continuous-run sample throughput rates of 12 h?1 are eralistic. 相似文献
27.
R. J. Pollard 《Hyperfine Interactions》1988,41(1):509-512
High quality Mössbauer spectra of γ-Fe2O3 particles have been analyzed in detail to determine the effects of overlapping patterns, quadrupole splitting, and applied magnetic fields. The results are discussed with regard to the use of Mössbauer spectroscopy to measure particle and magnetic moment orientation. Data were collected from two samples at 4.2–315K and with 6.1T longitudinal and 1.65T transverse magnetic fields applied. It is shown that electric field gradient effects alone are insufficient to account for the presence of ΔmI=0 lines when a large longitudinal field is applied. 相似文献
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29.
A survey of the metal-complexing reactions, as determined by reactions on chromatography paper, of 44 compounds with a substituted or modified 4-(2-pyridylazo)-resorcinol (PAR) or 1-(2-pyridylazo)-2-naphthol (PAN) structure is reported. 相似文献
30.