Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session E16: Physics of Weakly-Bound Nuclear SystemsInvited
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Sponsoring Units: DNP Chair: Hiro Iwasaki, Michigan State University Room: Washington 3 |
Saturday, January 28, 2017 3:30PM - 4:06PM |
E16.00001: Single-particle and collective motion in nuclear open quantum systems Invited Speaker: Kevin Fossez The properties of drip-line nuclei are profoundly affected by the environment of continuum states and the presence of decay channels. Their description requires the development of realistic theoretical approaches rooted in the open quantum system framework. However this formidable task presents many challenges and calls for closer collaborations between theorists and experimentalists. In this presentation a brief introduction to the problem of the description of weakly bound and unbound nuclei will be given with an emphasis on the relationship between nuclear structure and reactions. This will be illustrated by two recent investigations on the nuclei $^{11}$Be and $^{39}$Mg, where the role of the interplay between the collectivity and the continuum on single-particle structure has been studied. Finally the question of the existence of a nuclear system in the continuum is discussed for the case of the four-neutron system. [Preview Abstract] |
Saturday, January 28, 2017 4:06PM - 4:42PM |
E16.00002: Precision lifetime measurements in light exotic nuclei Invited Speaker: Elizabeth McCutchan A new generation of ab-initio calculations, based on realistic two- and three-body forces have had a profound impact on our understanding of nuclei. They have shed light on topics such as the origin of effective forces (like spin-orbit and tensor interactions) and the mechanisms behind cluster and pairing correlations. New precise data are required to both better parameterize the three body forces and to improve numerical methods. A sensitive probe of the structure of light nuclei comes from their electromagnetic transition rates. A refined Doppler Shift Attenuation Method (DSAM) will be outlined which is used to precisely measure lifetimes in light nuclei and helps to reduce and quantity systematic uncertainties in the measurement. Using this careful DSAM, we have made a series of precise measurements of electromagnetic transition strengths in Li isotopes, A$=$10 nuclei, and the exotic halo nucleus, $^{\mathrm{12}}$Be. Various phenomena, such as alpha clustering and meson-exchange currents, can be investigated in these seemingly simple systems, while the collection of data spanning stable to neutron-rich, allows us to probe the influence of additional valence neutrons. This talk will report on what has been learned, and the challenges that lie in the future, both in experiment and theory, as we push to describing and measuring even more exotic systems. [Preview Abstract] |
Saturday, January 28, 2017 4:42PM - 5:18PM |
E16.00003: Proton-decaying, light nuclei accessed via the invariant-mass method Invited Speaker: Kyle Brown Two-nucleon decay is the most recently discovered nuclear decay mode. For proton-rich nuclei, the majority of multi-proton decays occur via sequential steps of one-proton emission. Direct two-proton (2p) decay was believed to occur only in even-Z nuclei beyond the proton drip line where one-proton decay is energy forbidden. This has been observed for the ground states of around a dozen nuclei including $^{\mathrm{6}}$Be, the lightest case, and $^{\mathrm{54}}$Zn, the heaviest case. Direct 2p decay has also recently been observed for isobaric analog states where all possible 1p intermediates are either isospin allowed and energy forbidden, or energy-allowed and isospin forbidden. For light proton emitters, the lifetimes are short enough that the invariant-mass technique is ideal for measuring the decay energy, intrinsic width and, for multi-proton decays, the momentum correlations between the fragments. I will describe recent measurements of proton emitters using the invariant-mass technique with the High Resolution Array (HiRA). I will present a new, high-statistics measurement on the sequential 2p decay of excited states in $^{\mathrm{17}}$Ne. Measuring the momentum correlations between the decay fragments allow us to determine the 1p intermediate state through which the decay proceeds. I will present data on the isobaric-analog pair $^{\mathrm{8}}$C and $^{\mathrm{8}}$B$_{\mathrm{IAS}}$, which highlight the two known types of direct 2p decay. I will also present the first observation of $^{\mathrm{17}}$Na, which is unbound with respect to three-proton emission. Finally I will present a new measurement on the width of the first-excited state of $^{\mathrm{9}}$C and compare to recent theoretical calculations. [Preview Abstract] |
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