Session E1: Nuclear Physics I

Analysis of Phenomenological and Hybrid Optical Models for Deuterium Scattering at 100 MeV/u

The elastic and inelastic cross-section measurements, taken at the Research Center for Nuclear Physics, Osaka University, Japan, have been analyzed for a range of nuclei to the end of developing optical models for deuterium scattering. For the first time, formulations of optical models which explicitly account for nucleon-nucleon pairing interactions viz. a double folding formalism have been employed for elastic fitting and DWBA calculations for low lying discrete states. The validities of these models in the range of masses $24 [Preview Abstract]

Triaxial Nuclei Floppy or Rigid?

Triaxial nuclear shapes are interesting since they are so unusual in the nuclear chart.But whether the triaxial nuclei are soft or rigid in shape is still a question.Softness of triaxial nuclei has primarily been studied in even-even nuclei. We study softness of triaxiality in odd-mass nuclei, using the Core Quasi-Particle Model coupling an even-even core in Algebraic Collective Model with a quasi-particle in the spherical field. We want to know if the quasi-particle outside of the core will influence the rigidness of the core or not? And how the quasi-particle influences the core's properties.   

Alpha Cluster states in O

search for $\alpha $-cluster states is an open and interesting question in nuclear structure and has implications for the understanding of helium burning in stars. We carried out an experiment to explore $\alpha $-cluster states above the 4$\alpha $-decay threshold in via the ($\alpha $,n) reaction at the University of Notre Dame's Nuclear Science Laboratory. The experimental setup included four double-sided strip detectors with 256 channels to measure energies and angular distributions of charged particles and 12 deuterated liquid scintillators were used to detect neutrons in the angular range 22\textordmasculine \textordmasculine . By reconstructing reaction kinematics $\alpha $-cluster levels in can be obtained. The experimental setup and preliminary results will be presented. work was supported by the NSF under contract number PHY -- 1419765.   

Search for E0 transitions in $^{\mathrm{154,156}}$Gd

Transitions between nuclear states below a few MeV can occur through two processes: $\gamma $-emission and internal conversion. The E0 transition can only occur through internal conversion and is the only way to observe the "forbidden" transitions between two 0$+$ states. The even Gd isotopes have been found to have a substantial number of low-lying 0$+$ states. Determining the nature of these 0$+$ states remains one of the open questions in nuclear structure. Measuring the E0 transitions from these states is crucial for understanding. We have searched for E0 transitions between 0$+$ states in $^{\mathrm{154,156}}$Gd nuclei following the $^{\mathrm{152,154}}$Sm($\alpha $,2n) reactions by measuring conversion electrons using the Internal Conversion Electron Ball (ICEBall) array in coincidence with $\gamma $-rays using the GEORGINA detectors at the University of Notre Dame's Nuclear Science Laboratory. Details of the experimental setup and preliminary results will be presented.   

Lifetime Measurements in $^{162}$Dy

Historically, the rare-earth region of nuclei has been a fountainhead for nuclear structure phenomena. One of the more debated structure effects is the nature of excited 0+ bands in nuclei, and continues to be an oustanding challenge in nuclear structure physics; several interpretations exist, and we hope that lifetime measurements can help distinguish between them. $^{162}$Dy has an abundance of 0+ states with limited lifetime data; we have measured excitation functions, mean lifetimes, and angular distributions of gamma rays for excited states in $^{162}$Dy at the University of Kentucky Accelerator Laboratory. Low lying excited states were populated up to an excitation energy of E < 3.2 MeV, where we will discuss the implications of the lifetimes under this energy threshold. This work was supported by the NSF under contract numbers PHY-1068192, PHY-1205412, and PHY-0956310.   

Low-energy enhancement in gamma-strength function of rare-earth elements

The Oslo method is a tool for extracting level density and gamma-strength functions from experimental data. Typically applied to gamma spectra obtained with NaI detectors, it was limited to gamma energies above 1 MeV. However, recent application of the technique to data obtained using Compton suppressed clover detectors allowed for lowering that limit to 0.5 MeV and revealed a low energy enhancement (upbend) in the gamma-strength function of $^{151,153}$Sm isotopes. This a first observation of such feature in a heavy, deformed nucleus. Presented here will be results of an experiment utilizing the STARLiTeR setup at Texas A\&M University where (p,d) reaction was used to populate the excited states of the nuclei of interest. The impact of the present enhancement in the gSF in such heavy, deformed nuclei on the theoretical models of the upbend and the (n,$\gamma$) rates for the r-process will be discussed.