Session M6: Nuclei with 40 < A < 100

Isomeric character of the 4$^{+}_{1}$ state in $^{44}$S: Mechanisms of breaking of the N$=$28 shell

The N$=$28 nucleus $^{44}$S exhibits a rich structure of excitations which illustrates different mechanisms of breaking the N$=$28 shell. A Coulomb excitation measurement [1] and an implantation-decay experiment [2] established the coexistence of 2p2h-deformed and 0p0h-spherical configurations. A two-proton knockout reaction [3] indicated a 4$^{+}$ state which shell model calculations suggest is likely isomeric, prolate-deformed and formed from a 1p1h configuration. A recent two-proton knockout experiment measured the lifetime of this 4$^{+}$ state using the recoil distance method and the GRETINA array. Results for the lifetime of the 4$^{+}$ state will be presented and its implication for the mechanisms of breaking the N$=$28 shell will be discussed.\\[4pt] [1] T. Glasmacher \textit{et al.}, Phys.Lett. \textbf{B 395} (1997), 163 \newline [2] C. Force \textit{et al.}, Phys.Rev.Lett. \textbf{105}, 102501 (2010) \newline [3] D. Santiago-Gonzalez \textit{et al.} Phys.Rev. \textbf{C 83}, 061305 R (2012)   

Inverse Kinematic Proton Scattering of $^{49}$Ca

An inverse kinematic proton scattering experiment was performed using the Ursinus College liquid hydrogen target and a rare isotope beam containing $^{48,49}$Ca and recorded using the GRETINA-S800 detector system at the NSCL. A preliminary cross section for the lowest lying octupole vibration excitation in $^{49}$Ca was measured using efficiency corrected gamma ray counts yielded by fitting GEANT simulations to the measured GRETINA spectra.   

Polarized photon scattering of $^{52}$Cr: Determining the parity of dipole states

Observation of dipole states in nuclei are important because they provide information on various collective and single-particle nuclear excitation modes, e.g., pygmy dipole resonance (PDR) and spin-flip M1 resonance. The PDR has been extensively studied in the higher and medium mass region, whereas not much information is available around the low mass (A $\sim$ 50) region where, apparently,the PDR starts to form. The present photoresponse of $^{52}$Cr has been investigated to test the evolution of the PDR in a nucleus with a small number of excess neutrons as well as to look for spin-flip M1 resonance excitation mode. Spin-1 states in $^{52}$Cr between 5.0 to 9.5 MeV excitation energy were excited by exploiting fully polarized photons using the $(\gamma,\gamma^{'})$ nuclear resonance fluorescence technique, a completely model-independent electromagnetic method. The de-excitation $\gamma$-rays were detected using a HPGe array. The experiment was carried out using the HIGS facility at TUNL. Results of unambiguous parity determinations of dipole states in $^{52}$Cr will be presented.   

Shapes and structures in the neighborhood of $^{68}$Ni: levels in $^{69}$Cu

The study of the level structure of $^{68}$Ni$_{40}$ during the last 15 years has been intense, fueled by the presence of two excited 0$^{+}$ levels and a single excited 2$^{+}$ level below 2.6 MeV. [C. J. Chiara et al., Phys. Rev. C \textbf{86}, 041304 (R) (2012)] Recently, Tsunoda et al., have performed a series of calculations that indicate spherical, oblate, and prolate shapes for the ground, first excited 0$^{+}$ level at 1604 keV, and second excited 0$^{+}$ level at 2511 keV. [Y. Tsunoda, T. Otsuka, N. Shimizu, M. Honma, and Y. Utsuno, arXiv:1309.5851v1] One approach to gaining additional insight into these ideas is to examine the structure of $^{69}$Cu$_{40}$ that has a single proton coupled to $^{68}$Ni. In this presentation, new levels and transitions will be presented for $^{69}$Cu$_{40.42}$ and discussed in the context of these three proposed shapes. Excited states in these nuclei were populated through multinucleon-transfer reactions using beams provided by the ATLAS facility at Argonne National Laboratory and studied with Gammasphere. From these data, an estimate of the barrier height separating the oblate and prolate shapes will be deduced.   

New Decay Studies of $^{66}$Ga

High-energy $\gamma$ rays with energies up to 5.0 MeV are emitted in the radioactive decay of $^{66}$Ga (T$_{1/2}$=9.49 h). Thus, this radionuclide appears to be a suitable candidate for energy and efficiency calibrations of high-resolution, $\gamma$-ray spectrometers that are employed in studies of very neutron-rich nuclei which have large Q$_{\beta}$ values. In addition, accurate emission probabilities of this isotope are of interest to medical imaging applications, owing to the existence of large $\beta^{+}$ decay branches, which need to be characterized with better accuracy. Decay studies of $^{66}$Ga were initiated using the $\gamma$-ray spectroscopy technique. The source was produced by means of the $^{66}$Zn(p,n) reaction at a beam energy of 12 MeV. Singles and $\gamma-\gamma$ coincidences measurements were carried out using a single Ge detector and Gammasphere, respectively. The previously known $^{66}$Ga decay scheme was extended and many new $\gamma$ rays were placed in the daughter nuclide $^{66}$Zn.\\[4pt] The work at ANL was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. S. Kumar acknowledges support from the Indo-US Science and Technology Forum for the award of a Research Fellowship.   

Transition from collectivity to single-particle degrees of freedom from magnetic moment measurements in $^{82}_{38}$Sr and $^{90}_{38}$Sr

The $g$ factors of excited states in the unstable isotopes $^{82}$Sr and $^{90}$Sr were measured by the transient field technique. Beams of $^{78}$Kr and $^{86}$Kr from the K500 cyclotron at Texas A\&M University were accelerated to energies just above the Coulomb barrier on carbon to produce the strontium isotopes via an $\alpha$ particle pickup. We report on the $\alpha$ transfer reaction and on the simultaneous $g$ factor measurements of the Coulomb-excited Kr isotopes.   

The Checkerboard Model of the Nucleus

The Lach Checker Board Model (CBM) of the nucleus and the associated ESM predicts that nature has 5 generations of quarks not 3. The heaviest generation in the Extended Standard Model (ESM) has a t' quark of mass 65 GeV and a b' quark of 42.4 GeV. The lepton in this generation has a mass of 27 GeV. Part of this theory evolved because it appears that the quarks and lepton of each generation have masses related by the geometric mean. The Geometric mean of 65 and 27 is 42. Charge is conserved ($+$2/3 and -1 is -1/3). Details of how this theory evolved is found on my web site (http://checkerboard.dnsalias.net) or in the following references [T.M. Lach, Checkerboard Structure of the Nucleus, Infinite Energy, Vol. 5, issue 30, (2000); T.M. Lach, Masses of the Sub-Nuclear Particles, nucl-th/0008026, @http://xxx.lanl.gov/] One independent check of this CB model is that the wavelength of the ``up'' quark orbiting inside the proton at 84.8123{\%} the speed of light around the ``dn'' quark in the center turns out to be exactly one DeBroglie wavelength. This explains the mass of the proton and neutron and their magnetic moments. This along with the beautiful symmetric 2D structure of the He nucleus led to the evolution of this theory. One would expect a t'-anti t' meson of mass of about 130 GeV.