Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session K8: Nuclear Structure with A<100 |
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Sponsoring Units: DNP Chair: Michael Thoennessen, Michigan State University Room: Hyatt Regency Jacksonville Riverfront City Terrace 4 |
Sunday, April 15, 2007 1:15PM - 1:27PM |
K8.00001: The Cluster Structure of $^{18}$O E.D. Johnson, G.V. Rogachev, S. Brown, V.Z. Goldberg, A. Crisp, C. Fu, B.W. Green, K.W. Kemper, O. Momotyuk, B. Roeder Clustering phenomena are known to play an important role in the structure of light nuclei. It can be expected that these remarkable structures in the alpha conjugate systems influence the structure of their neighboring, non-alpha conjugate nuclei, forming molecular type structures [1]. Several experiments have recently indicated that two-center, molecular type structures, with one or two valence neutrons, exist in $^{22}$Ne, $^{21}$Ne, and $^{10}$Be [2,3,4]. Evidently, data on the cluster states in $^{18}$O may be very useful for better understanding the phenomenon in question. We performed a detailed study of the cluster structure in $^{18}$O by measuring the elastic scattering of $^{14}$C on $\alpha $-particles using the Thick Target Inverse Kinematics technique [5]. The analysis was done using a multi-level, multi-channel R-Matrix approach. The properties of the cluster configurations in $^{18}$O will be discussed, along with the influence of the low lying $\alpha $-cluster states on the astrophysically important $^{14}$C($\alpha $,$\gamma )$ reaction rate. [1] W. von Oertzen, Eur. Phys. J. A11 (2001) 403. [2] G.V. Rogachev, et al., Phys. Rev. C 64 (2001) 051302. [3] S. Thummerer, et al., J. Phys. G 29 (2003) 509. [4] M. Freer, et al., Phys. Rev. Lett. 96 (2006) 042501. [5] K.P. Artemov, et al., Sov. J. Nucl. Phys. 52 (1990). [Preview Abstract] |
Sunday, April 15, 2007 1:27PM - 1:39PM |
K8.00002: Structure of $^{21}$F from $^{14}$C-induced reactions M. Perry, S.L. Tabor, J. Pavan, A. Aguilar, P.C. Bender, I.J. Calderin, D.B. Campbell, W.T. Cluff, E. Diffenderfer, J. Fridmann, T.A. Hinners, C.R. Hoffman, K.W. Kemper, S. Lee, B.T. Roeder, C. Teal, Vandana Tripathi, M. Wiedeking, I. Wiedenh\"over $^{21}$F was populated at Florida State University from the $^{10}$Be($^{14}$C,t) and $^{9}$Be($^{14}$C,d) reactions at 21.4 MeV and 22.0 MeV, respectively. HPGe detectors were used to study the gamma decay scheme of $^{21}$F, and a segmemted particle telescope was used to detect the emitted particles from the compound nucleus for identification. New states were observed along with new gamma-ray transitions. Results will be compared with shell model calculations, previous experiments, and the systematics of other fluorine isotopes. [Preview Abstract] |
Sunday, April 15, 2007 1:39PM - 1:51PM |
K8.00003: Lifetimes of excited states in neutron rich $^{22}$F Sangjin Lee, S.L. Tabor, A. Aguilar, P.C. Bender, T.A. Hinners, C.R. Hoffmann, M. Perry, Vandana Tripathi $^{22}$F was populated from the $^{9}$Be($^{14}$C,p) reaction at $E_{\rm lab}$ = 22 MeV at the the Florida State University Superconducting Accelerator Laboratory. An 1848 $\mu$g/cm$^2$ thick $^{9}$Be target stopped both the recoiling $^{22}$F nuclei and the $^{14}$C beam without slowing the protons from the reaction very much. These protons were detected and identified with a segmented $\Delta E$-$E$ Si particle telescope. $\gamma$ rays were measured using Compton-suppressed high-purity germanium detectors at angles of 35$^\circ$,90$^\circ$, and 145$^\circ$ relative to the beam. Proton-$\gamma$ and proton-$\gamma$-$\gamma$ coincidences were used to analyze the data. Eight previously known $\gamma$-ray transitions were confirmed and three new $\gamma$-ray transitions were found. Lifetimes of 7 excited states in $^{22}$F were measured using the Doppler-shift Attenuation Method (DSAM). This work was supported in part by the National Science Foundation. [Preview Abstract] |
Sunday, April 15, 2007 1:51PM - 2:03PM |
K8.00004: Complimentary Approaches to the Study of T=2 30Al T.A. Hinners, Vandana Tripathi, S.L. Tabor, P.C. Bender, C.R. Hoffman, S. Lee, M. Perry, M. Wiedeking, P.F. Mantica, A.D. Davies, S.N. Liddick, W.F. Mueller, A. Stolz, B.E. Tomlin Excited states in $^{30}$Al were populated through the $^{14}$C($^{18}$O, pn$\gamma$)$^{30}$Al fusion evaporation reaction at an energy of 22 MeV at Florida State University. In addtion, $^{30}$Al was studied by the $\beta$-decay of $^{30}$Mg produced by the intermediate energy projectile fragmentation of $^{48}$Ca beam at 140 MeV/nucleon on $^{9}$Be at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. Through the $\beta$-decay results, the half-life of the parent nucleus, $^{30}$Mg, was found to be 315 $\pm$ 6 ms which is in good agreement with previous results. Also, the previously known low-lying $\gamma$ transitions were observed. In addtion, two new lines were observed leading to a new 1$^{+}$ state. The in-beam analysis yielded many new states that appear to have relatively high-spin ($\ge$ 4$^{+}$). Results, thus far, from both experiments are in good agreement with each other, shell model predictions, and previous work. This work was supported in part by the National Science Foundation. [Preview Abstract] |
Sunday, April 15, 2007 2:03PM - 2:15PM |
K8.00005: The $\beta$ and delayed-neutron decay properties of neutron rich $^{76-79}$Cu S.V. Ilyushkin, J.A. Winger, K.P. Rykaczewski, C.J. Gross, D. Shapira, R. Grzywacz, S.N. Liddick, C. Mazzocchi, S. Padgett, M.M. Rajabali, J.C. Batchelder, A. Korgul, W. Krol\'{a}s, E.F. Zganjar, A. Piechazek, C. Goodin, J.H. Hamilton Results of studies performed at the HRIBF on the $\beta$-decay of $^{76-79}$Cu isotopes are reported. Transmission through a charge exchange cell and isobar separator removed Zn from the ISOL beams and allowed fine tuning to obtain higher Cu concentrations. The $\beta$-delayed neutron probabilities of $^{76}$Cu and $^{77}$Cu were deduced from comparison of the intensities of $\gamma$ rays in the Zn daughter isotopes and found to be 4(1)\% and 38(4)\%, respectively. For $^{78}$Cu, the yrast decay sequence transitions at 730, 891, and 907 keV suggest the highest feeding is to the $6^+$ state with no population of the $8^+$ isomer. For the r-process critical nuclide $^{79}$Cu we observed for the first time the 730 keV $\gamma$ ray from the delayed-neutron branch thus solidifying this transition as the $2^+ \rightarrow 0^+$ transition in $^{78}$Zn. [Preview Abstract] |
Sunday, April 15, 2007 2:15PM - 2:27PM |
K8.00006: Neutron single-particle states and beta-delayed neutron branching ratios near $^{78}$Ni M.M. Rajabali, R. Grzywacz, S.N. Liddick, C. Bingham, I. Darby, C. Mazzocchi, K. Rykaczewski, J. Batchelder, T. Baumann, T. Ginter, P. Mantica, M. Karny, K. Miernik, M. Pfutzner, S.V. Ilyushkin, J. Winger, W. Krolas The measurement of low-energy excited states in $^{71-75}$Ni populated through the beta decay of $^{71-75}$Co isotopes was performed at the NSCL at MSU. The $^{71-75}$Co isotopes were obtained from the fragmentation of $^{86}$Kr beam, at 140 AMev, on a Be target. The experimental setup consisted primarily of a thick Double-sided Silicon Strip Detector for the correlation of implanted ions with their subsequent beta decays and the NSCL Segmented Germanium Array (SeGA) to monitor the emitted gamma rays. All detectors were read out with a new digital data acquisition system based on new generation Pixie16 produced by XIA and further developed at the University of Tennessee and Oak Ridge National Laboratory. Preliminary results of the experiment will be presented. [Preview Abstract] |
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