Experimental study of ^{84}Ga β decay: Evidence for a rapid onset of collectivity in the vicinity of ^{78}Ni (original) (raw)

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.

Experimental study ofGa84 βdecay: Evidence for a rapid onset of collectivity in the vicinity ofNi78

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.

Beta Decay of the Most Neutron-rich Isotopes Close to 78^{78}78Ni

Acta Physica Polonica B, 2015

In an experiment at the HRIBF, Oak Ridge National Laboratory, USA, we have investigated excited states in 86 Se populated in the beta-decay of 86 As. Several new transitions were identified. Preliminary results are presented.

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.

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.

β-decay of the neutron-rich nucleusN18

Physical Review C, 2005

The β-decay of 18 N has been studied using β-n and β-γ coincidence methods. The 18 N ions were produced by the fragmentation of the E/A = 68.8 MeV 22 Ne beam on a thick beryllium target. A newly constructed neutron detector system with wide energy detection range and low-energy detection threshold was used. The 619 ± 2 ms half-life of the 18 N β-decay was found to be in very good agreement with the previous measurements. Transitions to 11 β-delayed neutron emitting states in 18 O have been observed with a total branching ratio of 6.98 ± 1.46%. The Gamow-Teller β-decay strengths of 18 N to these levels were deduced and compared with the shell model calculations. The intensities of the strong γ-ray transitions in 18 O were found to be consistent with recent work.

Study of the N = 50 major shell effect toward 78Ni at PARRNe⋆

The European Physical Journal A, 2006

The γ-ray de-excitations following the β-decay of 83 Ga and the β-n decay of 84 Ga have been studied. The radioactive species were produced using the PARRNe on-line mass-separator installed at the IPN Orsay Tandem accelerator. Two γ-lines were attributed to 83 Ge with the aid of β-γ and γ-γ coincidences. The Z identification of the γ-lines was provided by time analysis of a buid-up/decay cycle. The excited levels of 83 Ge can be explained by the coupling of the single neutron state ν2d 5/2 to the first 2 + excitation of the 82 Ge core. PACS. 29.30.-h Spectrometers and spectroscopic techniques-21.10.-k Properties of nuclei; nuclear energy levels-23.20.Lv gamma transitions and level energies-27.50.+e 59 ≤ A ≤ 89 Production d'Atomes Radioactifs Riches en Neutrons.

Beta-decay of the N = Z nucleus 72 Kr

The European Physical Journal A - Hadrons and Nuclei, 2003

The beta-decay of the N = Z, even-even nucleus 72 Kr has been studied at the ISOLDE PSB facility at CERN. Measurements of βγ and βγγ coincidences have enriched the decay scheme of the daughter nucleus 72 Br with 27 new low spin levels. A more precise half-life of T 1/2 = 17.1(2) s has been determined. Strong feeding to the 72 Br ground state is established yielding an unambiguous J π = 1 + assignment for this state. Candidates for the 72 Br g.s. wave function are discussed in the framework of a self-consistent deformed mean-field calculation with SG2 Skyrme force and pairing correlations. A search for beta-delayed particle emission was made and an upper limit of 10 −6 for this decay branch obtained. The cumulated experimental level density of 1 + states has been fitted with the constant temperature formula. The comparison indicates that most likely all 1 + levels up to 1.2 MeV have been observed in this investigation. The corresponding nearest-neighbour level spacing does not follow a Poisson distribution. The Gamow-Teller strength distribution is compared, in terms of nuclear deformation, with different calculations made in the framework of the quasiparticle random phase approximation.

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.