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Åberg, S.

Publications and source records attributed to Åberg, S..

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Onset of high-spin rotational bands in the $N = Z$ nucleus 62 Ga

The fusion-evaporation reaction 28 Si + 40 Ca at 122 MeV beam energy was used to populate high-spin states in the odd-odd $N = Z$ nucleus 62 Ga. With the combination of the Gammasphere spectrometer and the Microball CsI(Tl) charged-particle detector array the decay scheme of 62 Ga was extended beyond 10 MeV excitation energy. The onset of band structures was observed. These high-spin rotational states are interpreted and classified by means of cranked Nilsson-Strutinsky calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Nuclear shape evolution based on microscopic level densities

Here, by combining microscopically calculated level densities with the Metropolis walk method, we develop a consistent framework for treating the energy and angular-momentum dependence of the nuclear shape evolution in the fission process. For each nucleus under consideration, the level density is calculated microscopically for each of more than five million shapes with a recently developed combinatorial method. The method employs the same single-particle levels as those used for the extraction of the pairing and shell contributions to the macroscopic-microscopic deformation-energy surface. Containing no new parameters, the treatment is suitable for elucidating the energy dependence of the dynamics of warm nuclei on pairing and shell effects. It is illustrated for the fission fragment mass distribution for several uranium and plutonium isotopes of particular interest.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Random matrix analysis of the monopole strength distribution in {sup 208}Pb

We study statistical properties of the 0{sup +} spectrum of {sup 208}Pb in the energy region E{sub x} ≤ 20 MeV. We use the Skyrme interaction SLy4 as our model Hamiltonian to create a single-particle spectrum and to analyze excited states. The finite-rank separable approximation for the particle–hole interaction enables us to perform the calculations in large configuration spaces. We show that while the position of the monopole resonance centroid is determined by one-phonon excitations of 0{sup +}, the phonon–phonon coupling is crucial for the description of the strength distribution of the 0{sup +} spectrum. In fact, this coupling has an impact on the spectral rigidity Δ{sub 3}(L) which is shifted towards the random matrix limit of the Gaussian orthogonal ensembles.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Systematic study of bubble nuclei in relativistic mean field model

We have theoretically studied potential bubble nuclei ({sup 20,22}O, {sup 34,36}Si, and {sup 46}Ar), which are experimentally accessible and have attracted several studies in the recent past. Relativistic mean field is employed in conjunction with the NL–SH parameter set. Our results show that among the possible candidates, {sup 22}Oand {sup 34}Si may be the most prominent candidates, showing significant depletion of density at the center, which could be verified experimentally in the near future with some of the experiments underway.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

The role of seniority-zero states in nuclear level densities

At low excitation energies seniority-zero states dominate the level density of K=0 bands in deformed even–even nuclei, while they play no role at higher excitation energies. We describe the level densities in a Fermi-gas model as well as in a combinatorial level-density model and compare to detailed experimental data for some rare-earth nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Selected spectroscopic results on element 115 decay chains

We observed thirty correlated α-decay chains in an experiment studying the fusion-evaporation reaction 48 Ca + 243 Am at the GSI Helmholtzzentrum fur Schwerionenforschung. The decay characteristics of the majority of these 30 chains are consistent with previous observations and interpretations of such chains to originate from isotopes of element Z = 115. High-resolution α-photon coincidence spectroscopy in conjunction with comprehensive Monte-Carlo simulations allow to propose excitation schemes of atomic nuclei of the heaviest elements, thereby probing nuclear structure models near the 'Island of Stability' with unprecedented experimental precision.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗