On the structure of 70, 72As
Abstract
The structure of the doubly odd nuclei 70, 72As has been investigated by the (p, nγ) reaction on70, 72Ge. From the energies and intensities of observed γ-transitions and from their coincidence relations the level schemes were constructed. The half-lives of several excited states were measured. Spin and parity assignments are based upon the analysis of the excitation functions and upon angular distributions of the γ-rays. The level schemes obtained are compared with the predictions of a quasiproton-quasineutron model with exact number projection. This model describes the differences between the spectra of 70, 72, 74, 76As and gives a good description for the properties of the states in 70, 72As. Values for the proton and neutron occupation probabilities have been derived. We conclude that it is not necessary to assume deformation for the lowest states and that the Schiffer force is successful in most cases as an effective proton-neutron interaction. Some exceptions are discussed.
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Nuclear Data Sheets for A = 70
2016, Nuclear Data SheetsSpectroscopic data for all nuclei with mass number A = 70 have been evaluated, and the corresponding level schemes from radioactive decay and reaction studies are presented. Since the previous evaluation, the half-life of 70Mn has been measured and excited states in 70Fe observed for the first time. Excited states in 70Ni have been more extensively studied while Coulomb excitation and collinear laser spectroscopy measurements in 70Cu have allowed for firm Jπ assignments. Despite new measurements, there remain some discrepancies in half-lives of low lying states in 70Zn. New measurements have extended the knowledge of high-spin band structures in 70Ge and 70As. This evaluation supersedes the prior A = 70 evaluation of 2004Tu09.
Nucleon-pair approximation to the nuclear shell model
2014, Physics ReportsAtomic nuclei are complex systems of nucleons–protons and neutrons. Nucleons interact with each other via an attractive and short-range force. This feature of the interaction leads to a pattern of dominantly monopole and quadrupole correlations between like particles (i.e., proton–proton and neutron–neutron correlations) in low-lying states of atomic nuclei. As a consequence, among dozens or even hundreds of possible types of nucleon pairs, very few nucleon pairs such as proton and neutron pairs with spin zero, two (in some cases spin four), and occasionally isoscalar spin-aligned proton–neutron pairs, play important roles in low-energy nuclear structure. The nucleon-pair approximation therefore provides us with an efficient truncation scheme of the full shell model configurations which are otherwise too large to handle for medium and heavy nuclei in foreseeable future. Furthermore, the nucleon-pair approximation leads to simple pictures in physics, as the dimension of nucleon-pair subspace is always small. The present paper aims at a sound review of its history, formulation, validity, applications, as well as its link to previous approaches, with the focus on the new developments in the last two decades. The applicability of the nucleon-pair approximation and numerical calculations of low-lying states for realistic atomic nuclei are demonstrated with examples. Applications of pair approximations to other problems are also discussed.
Nuclear Data Sheets for A = 72
2010, Nuclear Data SheetsExperimental data on ground- and excited-state properties for all known nuclei with mass number A = 72 have been compiled and evaluated. States populated in radioactive decay, as well as in nuclear reactions, have been considered. For these nuclei, level and decay schemes, as well as tables of nuclear properties, are given. This work supersedes the 1994 evaluation by W.-T. Chow and M.M. King (1994Ch45).
Nuclear Data Sheets for A = 74
2006, Nuclear Data SheetsNuclear spectroscopic information for known nuclides of mass number 74 (Co,Ni,Cu,Zn,Ga,Ge,As,Se,Br,Kr, Rb,Sr) with Z = 27 to 38 and N = 47 to 36 have been evaluated and presented together with adopted energies and Jπ of levels in these nuclei. No excited state data are yet available for 74Co, 74Cu and 74Sr. This evaluation supersedes previous full evaluations of A = 74 by 1987Si08 and 1976Ko07, and a midstream evaluation (published in update mode) by 1995Fa23 with a literature cutoff date of May 1994. Extensive new data have been included for most nuclides in the current revision of A = 74.
Nuclear data sheets for A = 70
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1. Very unstable nuclides, 70Ca, 70Sc, 70Ti, 70Cr, 70Rb, 70Sr have not been observed.
2. Half-life has been measured for 70Fe.
3. Decay of 70Co isomers has been studied.
4. A third isomer in 70Cu has been observed and decays for all three isomers have been studied.
5. A new decay scheme for 70Ni has been prepared.
6. New levels in 70Zn from 70Cu decay have been seen.
7. In 70As many more levels with better Jπ values have been reported.
8. 70Br ɛ decay to 70Se has been studied.
9. A new 70Br level scheme has been added.
Structure of <sup>72</sup>As nucleus
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Present address: Computer Centrum Limburg, Heerlen, the Netherlands.