382 research outputs found
Ultra high resolution stepper motors design, development, performance and application
The design and development of stepper motors with steps in the 10 arc sec to 2 arc min range is described. Some of the problem areas, e.g. rotor suspension, tribology aspects and environmental conditions are covered. A summary of achieved test results and the employment in different mechanisms already developed and tested is presented to give some examples of the possible use of this interesting device. Adaptations to military and commercial requirements are proposed and show the wide range of possible applications
Radioactive decays at limits of nuclear stability
The last decades brought an impressive progress in synthesizing and studying
properties of nuclides located very far from the beta stability line. Among the
most fundamental properties of such exotic nuclides, usually established first,
is the half-life, possible radioactive decay modes, and their relative
probabilities. When approaching limits of nuclear stability, new decay modes
set in. First, beta decays become accompanied by emission of nucleons from
highly excited states of daughter nuclei. Second, when the nucleon separation
energy becomes negative, nucleons start to be emitted from the ground state.
Here, we present a review of the decay modes occurring close to the limits of
stability. The experimental methods used to produce, identify and detect new
species and their radiation are discussed. The current theoretical
understanding of these decay processes is overviewed. The theoretical
description of the most recently discovered and most complex radioactive
process - the two-proton radioactivity - is discussed in more detail.Comment: Review, 68 pages, 39 figure
The ¹⁸⁰Lu beta decay to the ¹⁸⁰Hf 8⁻ isomeric state and the r-process formation of ¹⁸⁰Tasup(m)
Gamow-Teller Strength in the Region of Sn
New calculations are presented for Gamow-Teller beta decay of nuclei near
Sn. Essentially all of the Sn Gamow-Teller decay strength is
predicted to go to a single state at an excitation energy of 1.8 MeV in
In. The first calculations are presented for the decays of neighboring
odd-even and odd-odd nuclei which show, in contrast to Sn, surprisingly
complex and broad Gamow-Teller strength distributions. The results are compared
to existing experimental data and the resulting hindrance factors are
discussed.Comment: 12 pages (latex) and 2 figures available on reques
Alpha decay and proton-neutron correlations
We study the influence of proton-neutron (p-n) correlations on alpha-decay
width. It is shown from the analysis of alpha Q values that the p-n
correlations increase the penetration of the alpha particle through the Coulomb
barrier in the treatment following Gamow's formalism, and enlarges the total
alpha-decay width significantly.
In particular, the isoscalar p-n interactions play an essential role in
enlarging the alpha-decay width.
The so-called "alpha-condensate" in Z > 84 isotopes are related to the strong
p-n correlations.Comment: 5 pages, 6 figures, accepted for publication in Phys. Rev. C (R.C.
Proton drip-line nuclei in relativistic mean-field theory
The position of the two-proton drip line has been calculated for even-even
nuclei with in the framework of the relativistic mean-field
(RMF) theory. The current model uses the NL3 effective interaction in the
mean-field Lagrangian and describes pairing correlations in the
Bardeen-Cooper-Schrieffer (BCS) formalism. The predictions of the RMF theory
are compared with those of the Hartree-Fock+BCS approach (with effective force
Skyrme SIII) and the finite-range droplet model (FRDM) and with the available
experimental information.Comment: 18 pages, RevTeX, 2 p.s figures, to appear in Phys. Rev.
- decay of the M=-1 nucleus Zn studied by selective laser ionization
- decay of Zn has been studied for the first time. A new laser ion-source concept has been used to produce mass-separated sources for and - spectroscopy. The half-life of Zn was determined to be 86(18) ms. Comparisons are made with previous data from charge-exchange reactions. Our Gamow-Teller strength to the 1 state at 1051 keV excitation in Cu agrees well with the value extracted from a recent (He, t) study. Extensive shell-model calculations are presented
Quadrupole deformations of neutron-drip-line nuclei studied within the Skyrme Hartree-Fock-Bogolyubov approach
We introduce a local-scaling point transformation to allow for modifying the
asymptotic properties of the deformed three-dimensional Cartesian harmonic
oscillator wave functions. The resulting single-particle bases are very well
suited for solving the Hartree-Fock-Bogoliubov equations for deformed drip-line
nuclei. We then present results of self-consistent calculations performed for
the Mg isotopes and for light nuclei located near the two-neutron drip line.
The results suggest that for all even-even elements with =10--18 the most
weakly-bound nucleus has an oblate ground-state shape.Comment: 20 pages, 7 figure
Hindered E4 decay of the 12+ yrast trap in 52Fe
AbstractThe γ decay of the 12+ yrast trap in 52Fe has been measured for the first time. The two E4 γ-branches to the 8+ states are hindered with respect to other B(E4) reduced transition probabilities measured in the f7/2 shell. The interpretation of the data is given in the full pf shell model framework, comparing the results obtained with different residual interactions. It is shown that measurements of hexadecapole transition probabilities constitute a powerful tool in discriminating the correct configuration of the involved wavefunctions
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