Results 1 - 10 of 1341
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[en] We discuss a point-group-theory based method of searching for new regions of nuclear stability. We illustrate the related strategy with realistic calculations employing the tetrahedral and the octahedral point groups. In particular, several nuclei in the rare earth region appear as excellent candidates to study the new mechanism. (author)
[en] The experimental reduced alpha width values, delta2, in the rare-earth region have been calculated and analysed. The comparison of delta2 values for favoured transitions of even nuclei with those with odd nucleons allows us to study the modification of pairing correlation. The procedure used in the analysis takes into account the possible shape polarization by the odd nucleon
[en] The fabrication of the β = 0.12 half-wave resonator prototype at the Rare Isotope Science Project (RISP) is now complete, and the subsequent processing and the vertical test are expected to begin shortly. The details of the fabrication are reported in this paper. We describe the fabrication steps, together with the quality control effort, for the optimal performance of the cavity at the vertical test.
[en] Study of the energy level systematics can be highly rewarding as it may reveal new and interesting features. The authors present examples from the deformed rare-earth region, where such studies lead to useful results
[en] Garrett et al. systematically investigated band-crossing frequencies resulting from the rotational alignment of the first pair of neutrons (AB) in rare-earth nuclei. In that study, evidence was found for an odd-even neutron number dependence attributed to changes in the strength of neutron pairing correlations. The present paper carries out a similar investigation at higher rotational frequencies for the second pair of aligning neutrons (BC). Again, a systematic difference in band-crossing frequencies is observed between odd- and even- Er, Yb, Hf, and W nuclei, but in the BC case, it is opposite to the AB neutron-number dependence. These results are discussed in terms of a reduction of neutron pairing correlations at high rotational frequencies and of the effects of Pauli blocking on the pairing field by higher-seniority configurations. Also playing a significant role are the changes in deformation with proton and neutron numbers, the changes in location of single-particle orbitals as a function of quadrupole deformation, and the position of the Fermi surface with regard to the various Ω components of the neutron shell.
[en] The δ-pairing strengths for rare-earth nuclei are estimated from nuclear masses of odd and even systems. The masses are calculated for a variety of macroscopic and microscopic models. We use the BCS and Lipkin-Nogami methods, with a blocking effect in case of odd nuclei. The rms mass deviations obtained in different models are from 0.66 to 1.46. (author)
[en] A survey of other techniques used in the preparation of nuclear targets is first briefly discussed. These can be roughly classified as chemical, mechanical and physical proparations. Vacuum evaporation is the most generally used technique and will be discussed in detail. A typical system for high vacuum evaporation is described and the three main methods of heating the target material to evaporating temperatures are discussed (i.e. conduction heating, radio frequency heating and heating by means of electron-bombardment). Various electron-bombardment guns are compared in greater detail. Stages in the fabrication and mounting of self-supporting foils as thin as 5 μg/cm2 are described in detail, with emphasis given to the preparation of thin self-supporting carbon foils used as target backings and stripper foils. A technique for the preparation of relatively thick (1-10 mg/cm2), isotopically pure, rare-earth targets (Yb, Sm, Dy, Er, Nd, Gd, Lu) is given. The simultaneous reduction of the oxide and deposition of the metal is described. Final fabrication of the target by mechanically rolling the small head of condensed metal between strips of molybdenum, is described in detail. The need for, and achievement of, target purity and conservation of expensive materials, is emphasised and discussed. (author)