Study of the N = 50 major shell effect toward 78Ni at PARRNe⋆ (original) (raw)
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Probing nuclear structures in the vicinity of ^{78}Ni with β- and βn-decay spectroscopy of ^{84}Ga
Physical Review C, 2013
The decay of 84 Ga has been reinvestigated at the PARRNe online mass separator of the electron-driven installation ALTO at IPN Orsay. The nominal primary electron beam of 10 μA (50 MeV) on a 238 UC x target in combination with resonant laser ionization were used for the first time at ALTO. Improved level schemes of the neutron-rich 83,84 Ge (Z = 32) isotopes were obtained. The experimental results are compared with the state-of-the-art shell model calculations and discussed in terms of collectivity development in the natural valence space outside the 78 Ni core.
Study of the N=50 shell closure close to 78Ni
Brazilian Journal of Physics, 2004
The PARRNe (Production d'Atomes Radioactifs Riches en Neutrons) experimental program has been part of the recent R&D efforts for the design of the SPIRAL2 project at GANIL. The PARRNe2 setup installed at IPN-Orsay allows the use of the Tandem as a deuteron driver in order to produce mass separated fission fragment beams. The measured fission fragment yields proved to be high enough to undertake a series of β-decay experiments dedicated at studying the structure of proton-deficient nuclei close to N=50. We report here on two such experiments, the first being dedicated at the observation of the decay of 83 Ga→ 83 Ge (Z=32, N=51), 84 Ga→ 84 Ge (Z=32, N=52) and the second of the decay of 81 Zn→ 81 Ga (Z=31, N=50) allowing for the fist time the identification of a few γ lines with transitions in the daughter nuclei thus providing the material for a preliminary glimpse of their structure.
Physical Review C, 2009
γ -rays following the β and β-n decays of the very neutron rich 84 31 Ga 53 produced by the photofission of 238 U have been studied at the newly built ISOL facility of IPN Orsay: ALTO. Two activities were observed and assigned to two β-decaying states: 84 Ga g , I π = (0 − ) and 84 Ga m , I π = (3 − , 4 − ). Excitation energies of the 2 + 1 and 4 + 1 states of 84 32 Ge 52 were measured at E(2 + 1 ) = 624.3 keV and E(4 + 1 ) = 1670.1 keV. Comparison with HFB + GCM calculations allows to establish the collective character of this nucleus. The excitation energy of the 1/2 + 1 state in 83 32 Ga 51 known to carry a large part of the neutron 3s 1/2 strength was measured at 247.8 keV. Altogether these data allow to confirm the new single particle state ordering which appears immediately after the double Z = 28 and N = 50 shell closure and to designate 78 Ni as a fragile and easily polarized doubly-magic core.
Prompt γ rays in 77Ge and 75Ge after thermal neutron capture
The European Physical Journal A, 2012
The reactions 74 Ge(n, γ) and 76 Ge(n, γ) have been measured with cold neutrons generated by the research reactor FRM II near Munich, Germany. The γ rays have been detected by two Comptonsuppressed HPGe systems in single and coincidence mode. The number of identified prompt transitions and levels in 77 Ge was increased significantly and the decay scheme could be reconstructed for the first time. The decay scheme was also reconstructed for 68 prompt transitions in 75 Ge. Previously reported inconsistencies of the γ-ray intensities in the 77 Ge β decay could be resolved. In particular, the region around 2039 keV was investigated carefully, since the background to the neutrinoless double-beta decay of 76 Ge must be understood well for the upcoming Gerda and Majorana experiments.
The ALTO facility at IPN Orsay and study of neutron rich nuclei in the vincinity of 78Ni
Nuclear Physics A, 2007
The ALTO facility at IPN Orsay is based on a linear electron accelerator (50 MeV, 10μA) dedicated to the production of neutron rich radiactive beams by photofission of a thick uranium carbide target paced on an ISOL line. The construction of the facility has ended in december 2005 and the first on-line tests have been carried out in mid-2006. The production of fission fragments after separation have been measured and are similar to the calculated predictions. Previously, using the same ISOL line, neutron rich nuclei in the vincinity of 78 Ni have been produced and studied using the deuteron beam available at the Tandem accelerator in Orsay. First results on excited states in 83 32 Ge 51 and 81 31 Ga 50 have been obtained and discussed in the frame of the shell model.
Beta decay studies of the N=Z and waiting point nucleus 72 Kr
EPJ Web of Conferences, 2014
The β + /EC decay of 72 Kr has been studied by means of the Total Absorption gamma Spectroscopy technique in order to determine the Gamow-Teller strength B(GT) distribution. The comparison with theoretical predictions suggests a dominantly oblate deformation for the 72 Kr ground state. The de-excitation of low-energy excited states in 72 Br is studied via conversion electron spectroscopy. The conversion coefficients and multipolarities of 14 low-energy transitions are determined and the spin and parity of the levels involved are deduced.
Single-Neutron Excitations in Neutron-Rich 83Ge and 85Se
Physical Review C, 2007
The 2 H( 82 Ge, p) 83 Ge and 2 H( 84 Se, p) 85 Se reactions were studied with radioactive beams of 82 Ge and 84 Se at beam energies of E beam = 330 and 380 MeV, respectively. Excitation energies, proton angular distributions, and asymptotic normalization coefficients have been determined for the lowest lying states of 83 Ge and 85 Se. Spectroscopic factors have also been extracted under normal assumptions of the bound-state potential properties in the distorted waves Born approximation analysis. However, the peripheral character of the measurements leads to large uncertainties in this extraction. Shell-model calculations have been performed in the region above 78 Ni, comparing the single-particle properties of the even-Z, N = 51 nuclei up to 91 Zr and including 83 Ge and 85 Se. Direct-semidirect neutron capture calculations to 83 Ge and 85 Se have also been performed using the spectroscopic input from these (d, p) reaction measurements.
Decay studies of N ≈ Z nuclei from 75 Sr to 102 Sn
The European Physical Journal A - Hadrons and Nuclei, 2002
Neutron deficient nuclei near 100 Sn have been produced by fragmentation of a 1 · A GeV 112 Sn beam. The fragments were separated, identified and stopped in a highly segmented silicon strip detector stack. This detector measured the total energy of emitted β + -particles. γ-radiation was measured with surrounding detectors. The half-lives for many nuclides have been determined for the first time and give important information for the following topics: For the heaviest particle-stable odd-odd nuclei 90 Rh, 94 Ag and 98 In we observed for the first time fast β-decays, compatible with superallowed Fermi transitions and confirmed such decays for 78 Y, 82 Nb and 86 Tc. We have also observed long-lived T = 0 states in some of these nuclei. We measured the half-lives of all rp-process waiting-point nuclei from 80 Zr up to 92,93 Pd. In addition we find the proton drip line nucleus 77 Y to decay dominantly via β-decay. To study the Gamov-Teller strength in the β-decay near the doubly magic 100 Sn we measured the half-life, β-and γ-spectrum of 102 Sn. We propose a level scheme for the daughter nuclide 102 In and deduce the Gamov-Teller strength (BGT = 4.0 ± 0.6). This is one of the largest values known.
Decay studies of N ≈ Z nuclei from 75Sr to 102Sn
The European Physical Journal A, 2002
Neutron deficient nuclei near 100 Sn have been produced by fragmentation of a 1 • A GeV 112 Sn beam. The fragments were separated, identified and stopped in a highly segmented silicon strip detector stack. This detector measured the total energy of emitted β +-particles. γ-radiation was measured with surrounding detectors. The half-lives for many nuclides have been determined for the first time and give important information for the following topics: For the heaviest particle-stable odd-odd nuclei 90 Rh, 94 Ag and 98 In we observed for the first time fast β-decays, compatible with superallowed Fermi transitions and confirmed such decays for 78 Y, 82 Nb and 86 Tc. We have also observed long-lived T = 0 states in some of these nuclei. We measured the half-lives of all rp-process waiting-point nuclei from 80 Zr up to 92,93 Pd. In addition we find the proton drip line nucleus 77 Y to decay dominantly via β-decay. To study the Gamov-Teller strength in the β-decay near the doubly magic 100 Sn we measured the half-life, β-and γ-spectrum of 102 Sn. We propose a level scheme for the daughter nuclide 102 In and deduce the Gamov-Teller strength (BGT = 4.0 ± 0.6). This is one of the largest values known.
Decay Studies of Very Neutron Rich Nuclei Near 78Ni
Acta Physica Polonica B, 2008
The properties of beta -gamma and beta -delayed neutron emission from 76-79Cu and 83-85Ga were measured at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. Selected results on the decay properties of copper isotopes are briefly presented and discussed.