Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session J9: Nuclear Structure II |
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Sponsoring Units: DNP Chair: Adam Fritsch, Gonzaga University Room: 250A |
Sunday, April 17, 2016 10:45AM - 10:57AM |
J9.00001: Precision Measurement of $^{56}$Fe(n,n$\gamma )$ Cross Sections Using 14.1 MeV Neutrons Haoyu Wang, David Koltick Integral production cross sections for 846.8 keV and 1238.3 keV prompt gamma rays from 14.1 MeV neutrons interactions on $^{56}$Fe are reported. The experimental technique takes advantage of the 1.5 nanosecond coincidence timing resolution between the neutron production time and the gamma ray detection time to reject noise, together with the large 30{\%} solid angle gamma ray coverage. The scattering angle coverage with respect to the neutron beam direction extends from 60 degrees to 120 degrees. The neutron flux is measured using the detected associated alpha-particle from the D-T fusion reaction produced using an associated particle neutron generator. Present cross section measurements using other techniques with limited timing resolution and solid angle coverage are in agreement at neutron energies lower than 6 MeV. At higher neutron energies reported results can disagree by more than 20{\%}. The more accurate technique used in these measurements can distinguish between the differences in the present reported results at higher neutron energies. [Preview Abstract] |
Sunday, April 17, 2016 10:57AM - 11:09AM |
J9.00002: Structure above the $t_{1/2}$ = 6.85-h, 21/2$^+$ isomer in $^{93}$Mo C. J. Chiara, J. J. Carroll, G. J. Lane, S. S. Hota, A. J. Mitchell, N. Palalani, M. W. Reed Excited states in $^{93}$Mo were populated in the $^{90}$Zr($^{7}$Li,$p3n$) reaction at the Heavy-Ion Accelerator Facility of the Australian National University. The CAESAR array of nine coaxial HPGe detectors and two low-energy photon spectrometers (LEPSs) was used to detect the emitted gamma rays. Relative yields for population of the 21/2$^+$, $^{93m}$Mo state and neighboring reaction channels were determined from gamma-singles data for beam energies of 5 to 8 MeV/$A$. The level structure above the isomer has been expanded through gamma-gamma coincidence measurements. These results will be compared with high-spin structure of neighboring nuclei and with shell-model calculations. [Preview Abstract] |
Sunday, April 17, 2016 11:09AM - 11:21AM |
J9.00003: Study on nuclear structures of Te isotopes beyond $N=82$ shell closure Pilsoo Lee, Chun Sik Lee, Chang-Bum Moon Tellurium which has two valence protons above the $Z=50$ proton shell closure is well known for collective behavior in low-lying states. Therefore, Te isotopes are known to be a good test ground for studying nuclear collective modes but also the effect of neutron-proton interaction on the shell evolution with variation of neutron numbers owing to the valence protons above $Z=50$. For this reason Te isotopes always attract our attention, however, most available spectroscopic nuclear data of Te isotopes remains below $N=82$, and experimental data is severely limited above $N=82$. Meanwhile, recent study of $^{138}$Te by means of $\beta$-$\gamma$ spectroscopy with fission fragments of $^{238}$U has provided us with new clues on excited states in $^{138}$Te, and the new experimental result has proposed new excited states that were unexpected in the previous theoretical studies. This study aims at understanding structural evolution in Te isotopes above $N=82$ with respect to below $N=82$ including the new data set available today. In this presentation we discuss the nuclear structures and effective interactions in Te isotopes above $N=82$ based on the nuclear shell model and interacting boson approximations. [Preview Abstract] |
Sunday, April 17, 2016 11:21AM - 11:33AM |
J9.00004: Study of multiphonon $\gamma\gamma$-band Of $^{156}Gd$ through Modified Soft Rotor Formula Parveen Kumari, H. M. Mittal The structure of multiphonon $\gamma\gamma$-band of $^{156}Gd$ is investigated by using the Modified Soft Rotor Formula (MSRF). The Modified Soft Rotor Formula proposed by Gupta et al. [1] is given as: \begin{equation} E(I)=EK + \frac{\hbar^{2} I(I+1)}{2\theta(1+ \sigma I)}, \end{equation} where $\theta$ is moment of inertia, $\sigma$ is known as softness parameter and $EK$ is constant energy term. The calculated values of moment of inertia of $\gamma\gamma$-band are almost equal to the moment of inertia of $\gamma$-band. The study of K=2 $\gamma$-band and K=4 $\gamma\gamma$-band using MSRF yield good energy values. The small values of the softness parameter and positive values of moment of inertia are obtained for multiphonon band. The staggering pattern in $\gamma$-band and $\gamma\gamma$-band are also studied. Recently, the study of multiphoon $\gamma\gamma$-band in $^{112}Ru$ and isotopes of $Mo$ have been done in Ref. [2]. References: [1] J. B. Gupta , S. Sharma and V. Katoch, Pramana J. of Phys., 81, 75 (2013). [2] P. Kumari and H.M. Mittal, Physica Scripta, 90, 085304 (2015). [Preview Abstract] |
Sunday, April 17, 2016 11:33AM - 11:45AM |
J9.00005: Nuclear Structure and Quasi-Discrete Features populated in the $^{152,154}$Sm(p,t) Reactions P. Humby, C.W. Beausang, A. Simon, N. Cooper, E. Wilson, K. Gell, T. Tarlow, G. Vyas, T.J. Ross, R.O. Hughes, J.T. Burke, R.J. Casperson, J. Koglin, S. Ota, J.M. Allmond, M. McCleskey, E. McCleskey, A. Saastamoinen, R. Chyzh, M. Dag The $^{152,154}$Sm(p,t) reactions were used to investigate large, narrow, quasi-discrete structures observed in the triton energy spectra at excitation energies of 2-3~MeV. The experiment utilized a 25~MeV proton beam from the K-150 cyclotron at the Cyclotron Institute of Texas A\&M University and the outgoing charged particles and $\gamma$ rays were detected using the STARLiTeR array. This consists of a highly segmented $\Delta$E-E silicon telescope and six BGO shielded HPGe clover detectors. The angular distributions of the outgoing tritons populating the narrow structures are compared to those from both the population of low energy discrete states and the high energy continuum region. The fraction of strength in the structures accounted for by the observed discrete states and the total strength of the feature in neighboring isotopes are discussed. [Preview Abstract] |
Sunday, April 17, 2016 11:45AM - 11:57AM |
J9.00006: Nuclear shell evolution Ian Bentley The appearance and disappearance of nuclear shells and sub-shells has been at the forefront of recent nuclear theory and experimental efforts. This work extends a previously introduced method of structural analysis and applies it to protons in an attempt to provide a more complete understanding of shell structure in nuclei. Experimental observables including the mean square charge radius, as well as other spectroscopic and mass related quantities have been analyzed for shell structure features. A preliminary analysis using Nilsson coefficient fits of experimental quantities, such as odd mass spectra and B(E2) values, along isotopic chains will be discussed. The goal of this work is to provide a means of predicting shell structure far from stability. [Preview Abstract] |
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