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Greene, J P

Publications and source records attributed to Greene, J P.

15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Excited levels in odd-A silver isotopes populated rn fission of {sup 252}Cf

Excited levels in 111−121 Ag , odd-𝐴 isotopes populated following spontaneous fission of 252 Cf have been studied using high-fold 𝛾 coincidences measured with Gammasphere array of Compton-suppressed Ge spectrometers at Argonne National Laboratory. The experimental information on these nuclei reported before has been corrected and extended. In the work we discuss the evolution of triaxiality in odd-Ag nuclei. Relative positions of the 𝜋⁢𝑝1/2 and 𝜋⁢𝑔9/2 shells defining the 𝑍=40 gap when approaching the 𝑁=82 closure, the 𝜋⁢1/2+⁢[431] intruder bands, the three-quasiparticle configurations, and the so called 𝑗−1 anomaly in odd-Ag nuclei are also discussed.

Urban, W.↗
DOE OSTI2011

Gamma-ray coincidence and fast-timing measurements using LaBr{sub 3}(Ce) detectors and gammasphere

The performance of new scintillator detectors based on LaBr{sub 3}(Ce) technology was evaluated in conjunction with the Gammasphere spectrometer. Specifically, the lifetimes of states between 50 ps and 1 ns, populated in the decay of the {sup 177m}Lu isomeric state (T{sub 1/2} = 160 d), have been measured. Even though the decay scheme is rather complex, it is possible to perform precise measurements because of the superior energy resolution of the LaBr{sub 3}(Ce) detectors, compared to that of BaF{sub 2} scintillators, when used in combination with the power of the Gammasphere array to isolate a specific {gamma} cascade

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Gas cell targets for experiments with radioactive beams.

In this paper we discuss the properties of gas cell targets used for the production of radioactive beams via the in-flight technique as well as gas cell targets used for studies of nuclear reactions in inverse kinematics at the ATLAS heavy ion accelerator.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Fusion Reactions with the One-Neutron Halo Nucleus {sup 15}C

The structure of {sup 15}C, with an s{sub 1/2} neutron weakly bound to a closed-neutron shell nucleus {sup 14}C, makes it a prime candidate for a one-neutron halo nucleus. We have for the first time studied the cross section for the fusion-fission reaction {sup 15}C+{sup 232}Th at energies in the vicinity of the Coulomb barrier and compared it to the yield of the neighboring {sup 14}C+{sup 232}Th system measured in the same experiment. At sub-barrier energies, an enhancement of the fusion yield by factors of 2-5 was observed for {sup 15}C, while the cross sections for {sup 14}C match the trends measured for {sup 12,13}C.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Synthesis of heavy nuclei using damped collisions: A test

We have measured the angular distributions and production cross sections for the products of the reaction of 859-MeV (E{sub c.m.}=461.9 MeV) {sup 160}Gd with {sup 186}W. We detected fragments that stopped in the 5.775 mg/cm{sup 2} target as well as fragments emerging at 9 deg. - 17 deg., 17 deg. - 90 deg., and 90 deg. - 180 deg. We also made a chemical separation of the Pb isotopes formed in this reaction. An unusually large yield of trans-target reaction products near Z=79 was observed. We compare these observations with the recent predictions of Zagrebaev and Greiner for this reaction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Measurements of x-and {gamma}-ray emission probabilities in the {Beta}{sup -} decay of {sup 233} Pa.

X- and {gamma}-ray emission probabilities from the {beta}{sup -} decay of {sup 233}Pa were measured with planar (LEPS) and coaxial Ge detectors. A {sup 233}Pa source was produced after radiochemical separation from a {sup 237}Np sample in which the parent ({sup 237}Np) and daughter ({sup 233}Pa) nuclides were in secular equilibrium. The results are compared with previous measurements and data evaluations.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2010

Progress toward an EDM measurement in {sup225}Ra.

Permanent electric dipole moments (EDMs) in atoms or molecules are a signature of time-reversal and parity violation and represent an important window onto physics beyond the Standard Model. We are developing a next generation EDM search based on laser-cooled and trapped {sup 225}Ra atoms. Due to octupole deformation of the nucleus, {sup 225}Ra is predicted to be two to three orders of magnitude more sensitive to T-violating interactions than {sup 199}Hg, which currently sets the most stringent limits in the nuclear sector. We will discuss progress toward realizing a first EDM measurement for {sup 225}Ra.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Coulomb excitation of a {sup 242}Am isomeric target : E2, E3 strengths, rotational alignment, and collective enhancement.

A 98% pure {sup 242m}Am (K=5{sup -}, t{sub 1/2} = 141 years) isomeric target was Coulomb excited with a 170.5-MeV {sup 40}Ar beam. The selectivity of Coulomb excitation, coupled with the sensitivity of Gammasphere plus CHICO, was sufficient to identify 46 new states up to spin 18 {h_bar} in at least four rotational bands; 11 of these new states lie in the isomer band, 13 in a previously unknown yrast K{sup {pi}} = 6{sup -} rotational band, and 13 in a band tentatively identified as the predicted yrast K{sup {pi}} = 5{sup +} band. The rotational bands based on the K{sup {pi}} = 5{sup -} isomer and the 6{sup -} bandhead were populated by Coulomb excitation with unexpectedly equal cross sections. The {gamma}-ray yields are reproduced by Coulomb excitation calculations using a two-particle plus rotor model (PRM), implying nearly complete {Delta}K = 1 mixing of the two almost-degenerate rotational bands, but recovering the Alaga rule for the unperturbed states. The degeneracy of the 5{sup -} and 6{sup -} bands allows for precise determination of the mixing interaction strength V, which approaches the strong-mixing limit; this agrees with the 50% attenuation of the Coriolis matrix element assumed in the model calculations. The fractional admixture of the I{sub K}{sup {pi}} = 6{sub 6{sup -}} state in the nominal 6{sub 5{sup -}} isomer band state is measured within the PRM as 45.6{sub -1.1}{sup +0.3}%. The E2 and M1 strengths coupling the 5{sup -} and 6{sup -} bands are enhanced significantly by the mixing, while E1 and E2 couplings to other low-K bands are not measurably enhanced. The yields of the 5{sup +} band are reproduced by an E3 strength of {approx}15 W.u., competitive with the interband E2 strength. Alignments of the identified two-particle Nilsson states in {sup 242}Am are compared with the single-particle alignments in {sup 241}Am.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Rotational bands in odd-A Cm and Cf isotopes: Exploring the highest neutron orbitals

Rotational bands have been identified up to high spins ({approx_equal}28({h_bar}/2{pi})) in the odd-A nuclei {sup 247,249}Cm and {sup 249}Cf through inelastic excitation and transfer reactions around the Z=100 region where stability results from shell effects. The [620]1/2 Nilsson configuration in {sup 249}Cm is the highest-lying neutron orbital, from above the N=164 spherical subshell gap, for which high-spin rotational behavior has been established. The data allow for an unambiguous experimental assignment of configurations to the observed bands, unusual for odd-A nuclei near Z=100. The high-spin properties are described in terms of Woods-Saxon cranking calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Neutron-induced fission cross sections of short-lived actinides with the surrogate reaction method.

Neutron-induced fission cross sections for {sup 242,243}Cm and {sup 241}Am have been obtained with the surrogate reaction method. Recent results for the neutron-induced cross section of {sup 243}Cm are questioned by the present data. For the first time, the {sup 242}Cm cross section has been determined up to the onset of second-chance fission. The good agreement at the lowest excitation energies between the present results and the existing neutron-induced data indicates that the distributions in spin and parity of states populated with both techniques are similar.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Near-yrast, medium-spin, excited states of {sup 91}Rb, {sup 93}Rb, and {sup 95}Rb

The medium-spin structure of the nuclei {sup 93}Rb and {sup 95}Rb is studied following the neutron-induced fission of {sup 235}U at the PF1B neutron guide, using the FIFI spectrometer, and at the Lohengrin mass spectrometer of the Institut Laue-Langevin Grenoble. These nuclei, plus {sup 91}Rb, are also studied following the spontaneous fission of {sup 248}Cm and {sup 252}Cf sources, using the EUROGAM-II and Gammasphere detector arrays, respectively. A high-spin isomeric state, with a half-life of 111(11) ns, is found in {sup 93}Rb at an excitation energy of 4422.4 keV, which most likely corresponds to the fully aligned [{pi}(g{sub 9/2}) x {nu}(g{sub 7/2}h{sub 11/2})]{sub 27/2}{sup -} configuration. An analogous configuration is proposed for the 5297.9-keV level observed in {sup 91}Rb. A new E3 decay branch of the 1133.9-keV isomer in {sup 91}Rb is found, for which the rather low transition rate of B(E3)=3.8(10) W.u. is determined. The energy of the isomeric state of {sup 95}Rb is now proposed to be at 810.6 keV, with a spin of (9/2{sup +}), and its half-life determined to be T{sub 1/2}=94(7) ns. A cascade of prompt transitions is observed on top of the 810.6-keV isomer in {sup 95}Rb. The near-yrast structures of {sup 91}Rb, {sup 93}Rb, and {sup 95}Rb are compared to the results of shell-model calculations, which support the proposed 27/2{sup -} interpretation of states in {sup 91}Rb and {sup 93}Rb. An analogous 27/2{sup -} state is expected to occur in {sup 95}Rb, as a long-lived isomer at 3.24 MeV. No such isomeric decay could be observed in a measurement using the Lohengrin spectrometer, which shows that, if it exists, its population, following the fission of {sup 235}U, is at least four times lower than that of the analogous 27/2{sup -} isomer in {sup 97}Y.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗