Evidence of nonstatistical neutron emission following β decay near doubly magic Sn 132
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Engineering topics
Mazzocchi, C.
Publications and source records attributed to Mazzocchi, C..
In 133 : A Rosetta Stone for Decays of r -Process Nuclei
Not Available
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
β decay of neutron-rich 76 Cu and the structure of 76 Zn
In this work, the β decay of 76 Cu to the levels of 76 Zn was studied at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Lab (ORNL). A purified 76 Cu beam was developed and data were recorded for the decay of the A=76 decay chain using four high-purity germanium (HPGe) clover detectors at the Low-energy Radioactive Ion Beam Spectroscopy Station (LeRIBSS). In this measurement, data on γ-ray emission following β decay, including βγ and γγ coincidences, were collected and γγ spectra were analyzed to identify the statistically significant coincidences. From this analysis, we propose a level scheme for 76 Zn which contains a total of 59 energy levels up to 6.0 MeV containing 105 γ rays. We have identified an additional 53 γ rays associated with this decay which could not be place in the decay scheme due to insufficient coincidence information or no energy match to identified levels. No γ rays from states in 75 Zn fed in the delayed-neutron branch were observed even though other γ rays in the A=75 decay chain were observed. Spin and parity assignments are proposed for some levels based on comparison to systematics and shell model calculations.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
β -delayed charged-particle decay of Si 22 , 23
The β decay of 22,23 Si by emission of delayed charged particles was investigated in an experiment at the Cyclotron Institute of Texas A&M University by means of an optical-readout time-projection chamber. The previously-known decay of the two isotopes by β-delayed one- and two-proton emission was confirmed. Here for the first time, a new, rare, decay mode for 23 Si, β-delayed three-proton emission, was observed and β-delayed proton-α emission tentatively identified. Moreover, the β-decay pattern for the ground state of 23 Si was studied by means of multireference density-functional-rooted calculations.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Production of the most neutron-deficient Zn isotopes by projectile fragmentation of Kr 78
The cross sections for the production of three most neutron-deficient zinc isotopes, 54–56 Zn, in the projectile fragmentation of 78 Kr at 345 MeV/nucleon on a beryllium target, were measured. Although the results are smaller by over an order of magnitude from those obtained with a 58 Ni beam at 75 MeV/nucleon on a nickel target, the rates of reaction products are found to be larger in the case of high-energy fragmentation of 78 Kr. The experimental cross sections for the most neutron-deficient isotopes of even-Z nuclei between zinc and krypton were analyzed in the framework of the abrasion-ablation model. A very good agreement with the data was found when the nuclear masses predicted by a particular variant of the Hartree-Fock-Bogoliubov mass model were used. The prospects for the observation of more exotic isotopes in this region are discussed in context of 2p radioactivity.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
First β-decay spectroscopy of 135 In and new β-decay branches of 134 In
The β decay of the neutron-rich 134 In and 135 In was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number Z=50 above the N=82 shell. The β-delayed γ-ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three β-decay branches of 134 In were established, two of which were observed for the first time. Population of neutron-unbound states decaying via γ rays was identified in the two daughter nuclei of 134 In, 134 Sn and 133 Sn, at excitation energies exceeding the neutron separation energy by 1 MeV. The β-delayed one- and two-neutron emission branching ratios of 134 In were determined and compared with theoretical calculations. The β-delayed one-neutron decay was observed to be dominant β-decay branch of 134 In even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of 134 Sn. Transitions following the β decay of 135 In are reported for the first time, including γ rays tentatively attributed to 135 Sn. In total, six new levels were identified in 134 Sn on the basis of the βγγ coincidences observed in the 134 In and 135 Inβ decays. A transition that might be a candidate for deexciting the missing neutron single-particle 13/2 + state in 133 Sn was observed in both β decays and its assignment is discussed. Experimental level schemes of 134 Sn and 135 Sn are compared with shell-model predictions. Using the fast timing technique, half-lives of the 2 + , 4 + , and 6 + levels in 134 Sn were determined. From the lifetime of the 4 + state measured for the first time, an unexpectedly large B(E2;4 + → 2 + ) transition strength was deduced, which is not reproduced by the shell-model calculations.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Mapping of fragmented νf 5/2 →πf 7/2 transitions in the 73 Co→ 73 Ni decay
Excited states in 73 , 75 Ni were investigated through the β decay of 73 , 75 Co in an experiment performed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). The experimental results extended the level scheme of Ni 73 to 3.2-MeV excitation energy and provided the experimental information on excited states in Ni 75 . The β -delayed neutron branching ratio for Co 73 was obtained. Furthermore, the experimental results are discussed in comparison with shell-model calculations.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Time Projection Chamber (TPC) detectors for nuclear astrophysics studies with gamma beams
Gamma-Beams at the HIS facility in the USA and anticipated at the ELI-NP facility, now constructed in Romania, present unique new opportunities to advance research in nuclear astrophysics; not the least of which is resolving open questions in oxygen formation during stellar helium burning via a precise measurement of the 12C() reaction. Time projection chamber (TPC) detectors operating with low pressure gas (as an active target) are ideally suited for such studies. We look over the progress of the current research program and plans for the future at the HIS facility with the optical readout TPC (O-TPC) and the development of an electronic readout TPC for the ELI-NP facility (ELITPC).
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Search for α decay of Te 104 with a novel recoil-decay scintillation detector
A search for superallowed α decay of N = Z nuclei Te 104 and Xe 108 was carried out using a novel recoil-decay scintillator detector at the tandem accelerator facility at the Japan Atomic Energy Agency (JAEA). In this study, inorganic crystal scintillation material YAP:Ce (yttrium aluminum perovskite) coupled to a position-sensitive photomultiplier tube (PSPMT) was implemented for the first time in a radioactive decay experiment. Residues from the fusion-evaporation reaction Ni 58 + Fe 54 → Xe * 112 were separated by the JAEA Recoil Mass Separator (RMS) and implanted into the YAP:Ce crystal. α decays of neutron-deficient tellurium isotopes were identified and proton emission of I 109 was observed. The α -decay chain Xe 109 → Te 105 → Sn 101 was recorded with a time interval of 960 ns between two α pulses. Position localization in the crystal for decays and ions in the energy range from hundreds of keV to 60 MeV was achieved with an accuracy of 0.67 mm, proving that this detector is capable of making temporal and spatial correlations for fast decay events. No conclusive evidence was found for the decay chain Xe 108 → Te 104 → Sn 100 within 3 days of experiment. However, two events were observed with properties consistent with the reported observation at the Fragment Mass Analyzer (FMA), but with a separation between signals of less than 4 ns. The cross section limit of 130 pb was obtained for production of two events of Xe 108 , about an order of magnitude below the expectation based on earlier cross section measurements and the HIVAP fusion-evaporation code.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗