Beta decay of [sup 31,32]Na and [sup 31]Mg: Study of the [ital N]=20 shell closure

Journal Article · Tue Jun 01 04:00:00 EDT 1993 · Physical Review, C (Nuclear Physics); (United States)

DOI:https://doi.org/10.1103/PhysRevC.47.2502· OSTI ID:6497758

Klotz, G; Baumann, P; Bounajma, M; Huck, A; Knipper, A; Walter, G ^[1]; Marguier, G ^[2]; Richard-Serre, C ^[3]; Poves, A; Retamosa, J ^[4]

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1. Centre de Recherches Nucleaires, Universite Louis Pasteur, F-67037 Strasbourg (France) the Isolde Collaboration, CERN, 1211 Geneva 23 (Switzerland)
2. Institut de Physique Nucleaire, Universite Claude Bernard, F-69622 Villeurbanne (France) the Isolde Collaboration, CERN, 1211 Geneva 23 (Switzerland)
3. Institut National de Physique Nucleaire et de Physique des Particules, F-75013 Paris (France) the Isolde Collaboration, CERN, 1211 Geneva 23 (Switzerland)
4. Departamento de Fisica Teorica, C-XI, Universidad Autonoma, Cantoblanco, E-28049 Madrid (Spain)

The [sup 31,32]Na and [sup 31]Mg beta decays were studied at the CERN on-line mass separator ISOLDE by gamma, gamma-gamma, and neutron-gamma measurements. In the [sup 31]Na decay, the assignment of previously reported [gamma] transitions and the observation of a new level at 3760 keV lead to a revised decay scheme which is found in good agreement with a calculation including two-particle--two-hole configurations in the model space, as far as only low-lying levels of [sup 31]Mg are concerned. In the [sup 31]Mg[r arrow][sup 31]Al decay, a new decay scheme involves ten [beta] branches and three states are reported for the first time. While satisfactory agreement with theoretical calculations is observed for excitation energies in [sup 31]Al, a strong discrepancy is observed for the intensity of the ground-state [beta] branch, the experimental one being highly quenched as compared to theoretical expectations. Finally, new spectroscopic results have been obtained in the [sup 32]Na [beta] decay. A previously noninterpreted 1436 keV [gamma] ray is now assigned in the [sup 32]Mg scheme. The 240 keV ray is shown to arise from [sup 31]Mg produced in the one-neutron channel, and to be related to the decay of an intruder state at [ital E][sub [ital x]]=461 keV. The latter is partially fed from the 1390 keV level. Both nicely compare with theoretical predictions locating 1[h bar][omega] states at 0.40 MeV (7/2[sup [minus]]) and 1.57 MeV (11/2[sup [minus]]). The first experimental evidence for a [gamma] cascade in the descendant [sup 32]Al is also obtained.

• OSTI ID: 6497758
• Journal Information: Physical Review, C (Nuclear Physics); (United States), Journal Name: Physical Review, C (Nuclear Physics); (United States) Vol. 47:6; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

663210* -- Ground-State Radioactivity-- (1992-)
663220 -- Electromagnetic Transitions-- (1992-)
663530 -- Nuclear Mass Ranges-- A=20-38-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
ANGULAR MOMENTUM
BETA DECAY
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY
BETA-MINUS DECAY RADIOISOTOPES
COINCIDENCE METHODS
COUNTING TECHNIQUES
DECAY
ENERGY LEVELS
EVEN-ODD NUCLEI
GAMMA CASCADES
GAMMA SPECTROSCOPY
ISOTOPES
LIGHT NUCLEI
MAGNESIUM 31
MAGNESIUM ISOTOPES
MATHEMATICAL MODELS
MILLISEC LIVING RADIOISOTOPES
NEUTRON SPECTRA
NUCLEAR CASCADES
NUCLEAR DECAY
NUCLEAR MODELS
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
PARITY
PARTICLE PROPERTIES
RADIOISOTOPES
SHELL MODELS
SODIUM 31
SODIUM 32
SODIUM ISOTOPES
SPECTRA
SPECTROSCOPY
SPIN