Jon Charles Batchelder

Orbital dependent nucleonic pairing in the lightest known isotopes of tin

By studying the (109)Xe→(105)Te→(101)Sn superallowed α-decay chain, we observe low-lying states in (101)Sn, the one-neutron system outside doubly magic (100)Sn. We find that the spins of the ground state (J=7/2) and first excited state (J=5/2) in (101)Sn are reversed with respect to the traditional level ordering postulated for (103)Sn and the heavier tin isotopes. Through simple arguments and state-of-the-art shell-model calculations we explain this unexpected switch in terms of a transition from the single-particle regime to the collective mode in which orbital-dependent pairing correlations dominate.

New constraints on the 18F(p,α) 15O rate in novae from the (d, p) reaction

The degree to which the (p,gamma) and (p,alpha) reactions destroy 18F at temperatures 1-4x10^8 K is important for understanding the synthesis of nuclei in nova explosions and for using the long-lived radionuclide 18F, a target of gamma-ray astronomy, as a diagnostic of nova mechanisms. The reactions are dominated by low-lying proton resonances near the 18F+p threshold (E_x=6.411 MeV in 19Ne). To gain further information about these resonances, we have used a radioactive 18F beam from the Holifield Radioactive Ion Beam Facility to selectively populate corresponding mirror states in 19F via the inverse d(18F,p)19F neutron transfer reaction. Neutron spectroscopic factors were measured for states in 19F in the excitation energy range 0-9 MeV. Widths for corresponding proton resonances in 19Ne were calculated using a Woods-Saxon potential. The results imply significantly lower 18F(p,gamma)19Ne and 18F(p,alpha)15O reaction rates than reported previously, thereby increasing the prospect of observing the 511-keV annihilation radiation associated with the decay of 18F in the ashes ejected from novae.

Structure Of Rare-Earth Nuclei Around The Proton Drip Line

Decay studies on rare earth nuclei around the proton drip line have been performed by means of the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility in Oak Ridge. The proton emission from the odd‐odd N=77 isotone 146Tm was reinvestigated, resulting in the assignment of the 1.01 MeV proton line to the decay of a short‐lived 146Tm state. A new proton radioactivity of 144Tm was identified. The decays of isomeric levels in the N=77 isotones, 140Eu, 142Tb and 144Ho were remeasured using γ and electron detectors. The analysis of the structure of studied nuclei, which accounts for the coupling between the protons and neutrons and for core excitations, is presented.

High-precision B(E2) measurements of semi-magic Ni 58,60,62,64 by Coulomb excitation

J. M. Allmond,1 B. A. Brown,2,3 A. E. Stuchbery,4 A. Galindo-Uribarri,5,6 E. Padilla-Rodal,7 D. C. Radford,5 J. C. Batchelder,8 M. E. Howard,9 J. F. Liang,5 B. Manning,9 R. L. Varner,5 and C.-H. Yu5 1JINPA, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 2National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA 3Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA 4Department of Nuclear Physics, Australian National University, Canberra ACT 0200, Australia 5Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 6Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA 7Instituto de Ciencias Nucleares, UNAM, AP 70-543, 04510 Mexico, D.F., Mexico 8UNIRIB, Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831, USA 9Department of Physics and Astronomy, Rutgers University, New Brunswick, New Jersey 08903, USA (Received 13 May 2014; revised manuscript received 7 August 2014; published 15 September 2014)

β decay of 71 , 73 Co: Probing single-particle states approaching doubly magic 78 Ni

Low-energy excited states in 71,73Ni populated via the decay of 71,73Co were investigated in an experiment performed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). Detailed analysis led to the construction of level schemes of 71,73Ni, which are interpreted using systematics and analyzed using shell-model calculations. The 5/2 states attributed to the the f5/2 orbital and positive-parity 5/2+ and 7/2+ states from the g9/2 orbital have been identified in both 71,73Ni. In 71Ni the location of a 1/2 -decaying isomer is proposed, and limits are suggested as to the location of the isomer in 73Ni. The location of positive-parity cluster states are also identified in 71,73Ni. Beta-delayed neutron branching ratios obtained from this data are given for both 71,73Co. DOI: 10.1103/PhysRevC.85.034326 PACS number(s): 23.40. s, 21.10.Pc, 21.60.Cs, 27.50.+

β-γ and β-delayed neutron-γ decay of neutron-rich copper isotopes

The {beta}-decay properties of neutron-rich Cu isotopes produced in proton-induced fission of {sup 238}U were studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The data were collected using high-resolution online mass separation, reacceleration, and digital {beta}-{gamma} spectroscopy methods. An improved decay scheme of N = 49 {sup 78}Cu and the first observation of N = 50 {sup 79}Cu {beta}-delayed neutron decay followed by a gamma transition are reported. Spin and parity (5{sup -}) are deduced for {sup 78gs}Cu. The {beta}-delayed neutron branching ratios (P{sub {beta}n}) for the {sup 77}Cu and {sup 79}Cu precursors are analyzed with the help of nuclear structure models.

Digital Electronics For The Versatile Array Of Neutron Detectors At Low Energies

A χ2 minimization algorithm has been developed to extract sub‐sampling‐time information from digitized waveforms, to be used to instrument the future Versatile Array of Neutron Detectors at Low energies. The algorithm performance has been characterized with a fast Arbitrary Function Generator, obtaining time resolution better than 1 ns for signals of amplitudes between 50 mV and 1V, with negligible walk in the whole range. The proof‐of‐principle measurement of the beta‐delayed neutron emission from 89Br indicates a resolution of 1 ns can be achieved in realistic experimental conditions.

Isomer And Beta-Decay Studies Of Nuclei Near 78Ni

An experiment was performed at the National Superconducting Cyclotron Laboratory at Michigan State University to investigate β‐ and isomer decay properties of several isotopes in the vicinity of 78Ni. The identification of an (8+) isomer in 76Ni was confirmed and its deexcitation cascade identified; the β‐decay of 71–73Co was reinvestigated and that of 74Co studied for the first time. First evidence of β‐delayed neutron emission in neutron‐rich cobalt isotopes was also obtained. Preliminary results are reported.

Fine structure in proton emission from the deformed 141g.sHo 141mHo

Fine structure in proton emission from the deformed states 141g.s.Ho (T1/2 = 4.1 ms) and 141mHo (T1/2 = 7.4 μs) has been discovered at Oak Ridge by detecting fusion evaporation residues with the Recoil Mass Spectrometer, Si‐detectors and digital signal processing electronics. The branching ratios to the first 2+ excited state in 140Dy were measured to be Ipg.s.(2+) = 0.9±0.1% and Ipm(2+) = 1.7±0.5%. A comparison of the available calculations to the experimental values calls for further development of the theoretical models.

Towards new proton radioactivities with radioactive beams and digital signal processing

Abstract Particle radioactivity studies using the XIA DGF-4C digital signal processing units at the Recoil Mass Separator of Oak Ridge National Laboratory are presented. Proton emission signals were observed starting from 500 ns after recoil implantation. An energy threshold below 100 keV for particle detection was achieved. For the 145 Tm and 146 Tm decay, evidence for the fine structure in proton emission was obtained. An experiment to search for a new proton emitter 149 Lu is described as an example where the combination of a 56 Ni radioactive beam and digital signal processing is a major advantage.