J. C. Batchelder

Proton radioactivity from highly deformed nuclei.

Proton emission half-lives are calculated within the DWBA formalism for {sup 131}Eu and {sup 141}Ho assuming permanent quadruple deformation. The decay rates are consistent with a decay from either [411 3/2] or [413 5/2] Nilsson states for {sup 131}Eu and [523 7/2] Nilsson state for {sup 141}Ho.

Evidence for Gamow-Teller Decay of

The β-delayed neutron emission of ^{83,84}Ga isotopes was studied using the neutron time-of-flight technique. The measured neutron energy spectra showed emission from states at excitation energies high above the neutron separation energy and previously not observed in the β decay of midmass nuclei. The large decay strength deduced from the observed intense neutron emission is a signature of Gamow-Teller transformation. This observation was interpreted as evidence for allowed β decay to ^{78}Ni core-excited states in ^{83,84}Ge favored by shell effects. We developed shell model calculations in the proton fpg_{9/2} and neutron extended fpg_{9/2}+d_{5/2} valence space using realistic interactions that were used to understand measured β-decay lifetimes. We conclude that enhanced, concentrated β-decay strength for neutron-unbound states may be common for very neutron-rich nuclei. This leads to intense β-delayed high-energy neutron and strong multineutron emission probabilities that in turn affect astrophysical nucleosynthesis models.

^{78}

We have investigated the {beta} decay of the T=0, T{sub 1/2}{approx}2.2s, isomeric level in the self-conjugate odd-odd nucleus {sup 70}Br. The observed {beta}-delayed {gamma} rays in the daughter nucleus {sup 70}Se and the deduced decay properties of the isomeric level allow, in conjunction with results from the deformed shell model, a spin and parity assignment of J{sup {pi}}=9{sup +} and suggest a structure of {l_brace}{pi}[404]9/2{sup +}{nu}[404]9/2{sup +}{r_brace}9{sup +}. The allowed unhindered {beta} decay of the isomer, possibly oblate deformed, proceeds to four-quasiparticle states in {sup 70}Se.

Ni Core from Beta-Delayed Neutron Emission Studies

A new excited state at 2164 keV has been identified in 72Ni with tentative spin and parity of 4+ based on comparison to shell model calculations. This level is suggested to be populated via the ?-decay of an isomeric state in 72Co, and is postulated to be one of the key states that play a role in the disappearance of isomers in Ni. The known low-energy levels in 72Ni are compared with results of shell model calculations using the NR78 interaction to follow the seniority of the observed states. In addition, the half-life of the 8+ isomer in 76Ni has been measured as 630(90) ns and the full cascade of transitions from this isomer has been verified experimentally in this work.

{beta} decay of the T=0 isomer in the N=Z proton drip-line nucleus {sup 70}Br

Deformations and wave functions of proton‐radioactive nuclei are studied using measured fine structure properties of proton emission and microscopic theoretical models. The experimental data are available for 131Eu and 145Tm decays, as well as for 141gsHo, where an observation of fine structure in proton emission is reported for the first time.

decay of 72Co and microsecond isomers in even-mass neutron-rich nickel isotopes

An array for decay studies of neutron-rich nuclei has been commissioned for use at the UNISOR separator at Holifield Radioactive Ion Beam Facility. This array consists of three segmented clover Ge detectors, plastic scintillators, and a high-resolution (∼1 keV) Si conversion electron spectrometer. These detectors are mounted on a support that surrounds a moving tape collector. This system has been named clover array for radioactive decay studies. The detectors have been outfitted with digital flash ADCs (XIA DGFs) that fit the preamp signals, with built-in pileup rejection.

Fine structure in proton emission

Great progress has been made in the last 20 years in the study of proton emission from unstable nuclei, but the prospects for additional strides in the next several years are bright. The present main limitations on the study of proton radioactivity are related to the inability to produce copious quantities of nuclides beyond the proton drip line, and the difficulty of measuring proton radioactivity of a mass-separated nucleus in the first few microseconds of its existence. At the Holifield Facility we will attack the second of these limitations by using new signal processing CAMAC modules DGF-4C. Digitizing of the preamplifier signals should enable the analysis of a proton decay occurring at times even less than 1 microsecond after an implant in a strip detector. In the same process, the threshold energy at which we can make measurements will be lowered. These two things will hopefully enable the measurement of lower-energy, but faster decays of isotopes in the 100Sn region and below. For the latter regio...

The CARDS array for neutron-rich decay spectroscopy at HRIBF

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)

Prospects for future proton studies at HRIBF

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)

High-precisionB(E2)measurements of semi-magicNi58,60,62,64by Coulomb excitation

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.