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991.
992.
The internal conversion process of theM1+E 2 mixed 279 keVγ-ray transition in the decay of203Hg has been reinvestigated. The emission rate of theK-shell internal conversion electrons was determined with an electron X-ray coincidence measurement using a magneticΒ-spectrometer and a Si(Li) detector of high energy resolution. Conversion electron ratios were obtained from electron spectra recorded as a function of momentum. The disintegration rate has been taken from measurements with a calibrated NaI(Tl)γ-ray spectrometer. Following results have been deduced: α=0.2279±0.0024, α K =0.1653±0.0017, α L =0.0475±0.0013,K/(L+M+?)=2.64±0.03,K/L=3.48±0.12,L/(M+N+ ?)=3.14±0.12. On the basis of the experimental results on theK-shell internal conversion coefficient,α k , and the conversion ratioK/(L+M+?) the penetration effect on the internal conversion of theM1 part and the mixing ratio,δ 2, of the 279 keVγ-ray transition in203Tl have been studied. Calculations were made using Hager and Seltzer's formalism and their theoretical internal conversion coefficients. The results are consistent with a mixing ratio ofδ 2=1.32±0.11 and a penetration parameter ofλ=6.8 ±0.8. 相似文献
993.
994.
K. Hansen J. T. Khoury M. L. Homer F. E. Livingston R. L. Whetten 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,26(1):187-188
Large sodium clusters, up ton=21, generated by a low-temperature modification of the laser ablation gas jet source were ionized with two photons of visible radiation from an amplified picosecond dye-laser system. 相似文献
995.
996.
997.
The one-shell SU(3) energies are given and the corresponding level density is calculated approximately by use of a distribution function for the SU(3) quantum numbers. The calculation is extended to include many shells by a renormalization procedure and an effective one-shell interaction. The traditional level density is then obtained from the related mean-field hamiltonian which corresponds to a deformed harmonic oscillator potential. Various rotational enhancement factors are considered. Numerical results, are obtained and comparisons between the SU(3) and the traditional level densities allow the first computation of the energy dependence of the rotational enhancement factor. A transition from axial to spherical level density is found. A simple parametrization is suggested in terms of a deformation-dependent half-value energy and a transition width. 相似文献
998.
Patricia Murasecco-Suardi Esther Oliveros Andr M. Braun Hans-Jürgen Hansen 《Helvetica chimica acta》1988,71(5):1005-1010
The near-infrared luminescence of singlet oxygen (1O2) has been measured in order to determine the efficiency of 1O2 quenching by two carotenoid compounds, β-carotene and canthaxanthin. 1H-Phenalen-1-one and rose bengal have been used as photosensitizers in those steady-state luminescence experiments. Stern-Volmer analysis of the 1O2 luminescence in solutions of CCl4 and CD3OD, containing different concentrations of the carotenoids, has shown a very efficient quenching by canthaxanthin. The rate constants are about a factor of 2 below the diffusion limited values for the given solvents, confirming earlier results in benzene. In comparison, the efficiency of 1O2 quenching by β-carotene is slightly lower than that by canthaxanthin in non-polar solvents and is reduced by an order of magnitude in CD3OD, due to the aggregation of this quencher. 相似文献
999.
1000.
A. V. Bobylev Frank A. Maaø Alex Hansen E. H. Hauge 《Journal of statistical physics》1997,87(5-6):1205-1228
The classical Lorentz model for charged noninteracting point particles in a perpendicular magnetic field is reconsidered in 2D. We show that the standard Boltzmann equation is not valid for this model, even in the Grad limit. We construct a generalized Boltzmann equation which is, and solve the corresponding initial value problem exactly. By an independent calculation, we find the same solution by directly constructing the Green function from the dynamics of the model in the Grad limit. From this solution an expression for the diffusion tensor, valid for arbitrary short-range forces, is derived. For hard disks we calculate the diffusion tensor explicitly. Away from the Grad limit a percolation problem arises. We determine numerically the percolation threshold and the corresponding geometric critical exponents. The numerical evidence strongly suggests that this continuum percolation model is in the universality class of 2D lattice percolation. Although we have explicitly determined a number of limiting properties of the model, several intriguing open problems remain.It is with great pleasure we include this paper in the issue honoring Matthieu Ernst, who not only shares our love for kinetic theory, but who also contributed so much to its modern development. 相似文献