Single-particle and collective motion for proton-rich nuclei in the upperpfshell

Abstract

Based on available experimental data, a new set of Nilsson parameters is proposed for proton-rich nuclei with proton or neutron numbers 28 ≤ N ≤ 40. The resulting single-particle spectra are compared with those from relativistic and non-relativistic mean field theories. Collective excitations in some even-even proton-rich nuclei in the upper pf shell are investigated using the Projected Shell Model with the new Nilsson basis. It is found that the regular bands are sharply disturbed by band crossings involving 1g 9/2 neutrons and protons. Physical quantities for exploring the nature of the band disturbance and the role of the 1g 9/2 single-particle are predicted, which may be tested by new experiments with radioactive beams.21.10. Pc, 21.10.Re, 21.60.Cs, 27.50.+e The nuclear shell model has been successful in the description of nuclear structure. Thanks to the increasing power of computation, exact diagonalizations in the full pf shell has become possible in recent years [1]. An immediate application has been seen in nuclear astrophysics [2,3], where knowledge about detailed nuclear structure is important in understanding the nuclear processes that govern those violent astrophysical phenomena such as nova and supernova explosions, or X-ray bursts.Nuclear structure information is thought to be important also in the study of the nuclear processes occurring on the astrophysical rapid proton capture or rp-process [4,5], which may be relevant to nova explosions or Xray bursts. The rp-process path lies close to the proton drip line in the chart of nuclides. There, compound nuclei are formed at very low excitation energies and therefore at low level densities, which does not justify HauserFeshbach calculations. Thus, detailed nuclear structure information is required when studying the nuclear processes. One hopes that radioactive beams will provide us with the information eventually, but one has to rely on theoretical calculations at present. To obtain detailed nuclear structure, advanced shell model diagonalization methods, which can give explicitly spectroscopy and matrix elements for all kinds of nuclei (even-even, odd-A and odd-odd), are of particular importance.The Projected Shell Model (PSM) [6] is a shell model diagonalization carried out in a projected space determined by a deformed Nilsson-BCS basis. This kind of shell model truncation is highly efficient if the singleparticle (SP) basis is realistic because the basis already contains many correlations [6]. It has been shown that the PSM can describe the spectra and electromagnetic transitions in normally deformed [6], superdeformed [7,8], and transitional nuclei [9]. One can further calculate the nuclear matrix elements for astrophysical processes such as direct capture and decay rates. One advantage of the PSM is that it can easily handle heavy, well-deformed nuclear systems. This can be important for the structure study of significantly deformed nuclei (Z = 36 − 40) on the rp-process path, for which the current large-scale shell model diagonalizations are...

Collective excitations and shape changes inY80

“…On the other hand, calculations with deformations larger than ⑀ 2 = 0.311 provide increased Q t values at the cost of worse agreement with the experimental energy spacings and B͑M1͒ values. At any rate, since B͑M1͒ strengths are sensitive to the single-particle attributes of the nuclear wave function, comparisons between the PSM predictions and the current experimental results can be used to reexamine the Nilsson model parameters appropriate for nucleon numbers in this mass region [51], as was done recently for proton-rich nuclei in the upper fp shell [52].…”

Particle alignments and shape change inGe66andGe68Hasegawa1, Kaneko2, Mizusaki3 2005Phys. Rev. C150170View full textAdd to dashboardCite

“…Our model reproduces well the changes of the moments of inertia for these three sequences of positive-parity states. The agreement with the experimental moments of inertia is much better than that of the total Routhian surface (TRS) calculations [6] and that of the projected shell model [31]. This indicates that our wave functions are better than those of the TRS calculations.…”

High-K isomer and the rotational properties in the odd-Z neutron-rich nucleus M163Eu *

“…To reflect the shell changes in the exotic mass region, an early attempt was made by empirically adjusting the Nilsson parameters from their standard values, see for example Refs. [20,22,23].…”