个人简介

B.S. Chemistry, 2001, Texas A&M Univ. Ph.D., Chemical Physics, 2004, Michigan State Univ. Faculty, 2009 – Present, National Superconducting Cyclotron Laboratory

研究领域

Chemical Physics Nuclear Physical

(Research Description PDF - 510 kb) Experimentally identifying changes in the structure of the atomic nucleus with unstable combinations of protons and neutrons is the focus of research in my group. The changes are the result of evolving single-particle level configurations as a progression is made from stability towards more exotic nuclei and leads to specific observables in the low-energy level structure of a nucleus. Decay spectroscopy provides a sensitive and selective means to populate and study low-energy excited states of daughter nuclei and a variety of different decay modes can be exploited depending on the nucleus of interest. Radioactive atoms with a large ratio of neutrons to protons are produced and isolated at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The atoms are then delivered to an experimental station for characterization through decay spectroscopy. The beta-decay experiments utilize small samples, sometimes fewer than one thousand individual atoms delivered over the course of multiple days. The atoms themselves rapidly decay away with half-lives on the order of hundreds of milliseconds or less. Depending on the energy of the state populated in the daughter nucleus, beta-delayed radiation can be observed, such as gamma rays, neutrons (from a neutron-rich nucleus), or protons (from a neutron deficient nucleus). Altogether, beta decay spectroscopy can provide the half-life of the parent decaying state, the low-energy structure of the daughter nucleus, and the intensity distribution of the decays to each final state in the daughter from which the structure of the nuclei involved can be inferred. Recent experimental progress has focused on nuclei near . The Ni isotopes are expected to be spherical and the spin, parity, and energy of excited levels in the two isotopes 67Ni and 69Ni can be used to determine the important single-particle states contributing to the structure of nuclei in this region. Upon the removal of one or three protons from either 67Ni or 69Ni the structure of the respective Co or Mn isotopes changes dramatically as indicated in the figure below. Two nuclear shapes have been tentatively identified in the low-energy structure of the Co and Mn isotopes The development of new detectors and techniques is critical to improving the sensitivity of the experimental system enabling access to increasingly exotic nuclei. The implementation of a digital acquisition system in the detection of alpha decays was critical for the detection of the long-lived isomeric states in the Mn isotopes shown in the figure. In addition to digital electronics, a new planar Ge detector is being developed for decay spectroscopy experiments and the two improvements combined offer both increased detection efficiencies and the ability for novel experiments. The low-energy level structure of Co and Mn isotopes with 39 or 41 neutrons. Half-lives, where appropriate, and tentative spins and parities are shown for each state. Further, a tentative identification of the shape of the nucleus associated with levels in the Co and Mn isotopes is given to the right of the states. A circle indicates spherical and an oval represents deformed.

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Low-energy structure of 2766Co39 and 2768Co41 populated through β decay, S.N.Liddick, B.Abromeit, A.Ayres, A.Bey, C.R.Bingham, M.Bolla, L.Cartegni, H.L.Crawford, I.G.Darby, R.Grzywacz, S.Ilyushkin, N.Larson, M.Madurga, D.Miller, S.Padgett, S.Paulauskas, M.M.Rajabali, K.Rykaczewski, S.Suchyta, Phys.Rev. C 2012, 85, 014328. Algorithms for Pulse Shape Analysis Using Silicon Detectors, S.N. Liddick, S. Suchyta,B. Abromeit, A. Ayres, A. Bey, C.R. Bingham, M. Bolla, M. Carpenter, L. Cartegni, C. Chiara, H. L. Crawford, I. G. Darby, R. Grzywacz, G. Gurdal, S. Ilyushkin, A. Klose, N. Larson, M. Madurga, E. McCutchan, D. Miller, S. Padget, S. Paulauskas, J. Pereira, M. M. Rajabali, K. Rykaczewski, A. Schneider, S. Vinnikova, W. B. Walters, and S. Zhu, Nucl. Instrum. Methods Phys. Res. A, 2012, 669, 70. Shape Coexistence along N = 40, S.N. Liddick, S. Suchyta, B. Abromeit, A. Ayres, A. Bey, C.R. Bingham, M. Bolla, M.P. Carpenter, L. Cartegni, C.J. Chiara, H.L. Crawford, I.G. Darby, R. Grzywacz, G. Gurdal, S. Ilyushkin, N. Larson, M. Madurga, E.A. McCutchan, D. Miller, S. Padgett, S.V. Paulauskas, J. Pereira, M.M. Rajabali, K. Rykaczewski, S. Vinnikova, W.B. Walters, S. Zhu, Phys. Rev. C 2011, 84, 061305. Orbital Dependent Nucleonic Pairing in the Lightest Known Isotopes of Tin, I.G.Darby, R.K.Grzywacz, J.C.Batchelder, C.R.Bingham, L.Cartegni, C.J.Gross, M.Hjorth-Jensen, D.T.Joss, S.N.Liddick, W.Nazarewicz, S.Padgett, R.D.Page, T.Papenbrock, M.M.Rajabali, J.Rotureau, K.P.Rykaczewski, Phys.Rev.Lett. 2010, 105, 162502. Discovery of 109Xe and 105Te: Superallowed α Decay near Doubly Magic 100Sn, S.N.Liddick, R.Grzywacz, C.Mazzocchi, R.D.Page, K.P.Rykaczewski, J.C.Batchelder, C.R.Bingham, I.G.Darby, G.Drafta, C.Goodin, C.J.Gross, J.H.Hamilton, A.A.Hecht, J.K.Hwang, S.Ilyushkin, D.T.Joss, A.Korgul, W.Krolas, K.Lagergren, K.Li, M.N.Tantawy, J.Thomson, J.A.Winger, Phys.Rev.Lett. 2006, 97, 082501.