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We have measured the $ \beta$ -decay half-lives of 16 neutron-deficient nuclei with $ T_{z} = -1/2$ and -1 , ranging from chromium to germanium. They were produced in an experiment carried out at GANIL and optimized for the production of$^{58}$Zn , for which in addition we present the decay scheme and absolute Fermi and Gamow-Teller transition strengths. Since all of these nuclei lie on the rp -process pathway, the $ T_{1/2}$ values are important ingredients for the rp -process reaction flow calculations and for models of X-ray bursters.

This paper concerns the experimental study of the β decay properties of few proton-rich fp -shell nuclei. The nuclei were produced at GANIL in fragmentation reactions, separated with the LISE spectrometer and stopped in an implantation detector surrounded by Ge detectors. The β -delayed gammas, β -delayed protons and the exotic β -delayed gamma-proton emission have been studied. Preliminary results are presented. The decay of the T z = − 2 nucleus 56 Zn has been studied in detail. Information from the β -delayed protons and β -delayed gammas has been used to deduce the decay scheme. The exotic beta-delayed gamma-proton decay has been observed for the first time in the fp -shell. The interpretation of the data was made possible thanks to the detailed knowledge of the mirror Charge Exchange (CE) process and the gamma de-excitation of the states in 56 Co, the mirror nucleus of 56 Cu.

We have studied the β decay of the Tz=−1, f7/2 shell nuclei Ni54, Fe50, Cr46, and Ti42 produced in fragmentation reactions. The proton separation energies in the daughter Tz=0 nuclei are relatively large (≈4–5 MeV) so studies of the γ rays are essential. The experiments were performed at GSI as part of the Stopped-beam campaign with the RISING setup consisting of 15 Euroball Cluster Ge detectors. From the newly obtained high precision β-decay half-lives, excitation energies, and β branching ratios, we were able to extract Fermi and Gamow-Teller transition strengths in these β decays. With these improved results it was possible to compare in detail the Gamow-Teller (GT) transition strengths observed in beta decay including a sensitivity limit with the strengths of the Tz=+1 to Tz=0 transitions derived from high resolution (3He,t) reactions on the mirror target nuclei at RCNP, Osaka. The accumulated B(GT) strength obtained from both experiments looks very similar although the charge exchange reaction provides information on a broader energy range. Using the “merged analysis” one can obtain a full picture of the B(GT) over the full Qβ range. Looking at the individual transitions some differences are observed, especially for the weak transitions. Their possible origins are discussed. (Less)

The magnetic dipole G_M(Q^2), electric quadrupole G_E(Q^2), and Coulomb quadrupole G_C(Q^2) form factors, describing the spin-3/2 to spin-1/2 electromagnetic transitions, are investigated within the light cone QCD sum rules. The Q^2 dependence of these form factors, as well as ratios of electric quadrupole and Coulomb quadrupole form factors to the magnetic dipole form factors are studied. We also compare our results on the magnetic dipole form factor with the prediction of the covariant spectator quark model., 20 pages, 10 figures, LaTeX formatted

Y. Oktem,1 D. L. Balabanski,2 B. Akkus,1 L. Amon Susam,1 L. Atanasova,2 C. W. Beausang,3,4 R. B. Cakirli,1,5 R. F. Casten,3 M. Danchev,6,7 M. Djongolov,6,7 E. Ganioglu,1 K. A. Gladnishki,7 J. Tm. Goon,8 D. J. Hartley,6,9 A. A. Hecht,3,10 R. Krucken,3,11 J. R. Novak,3 G. Rainovski,7 L. L. Riedinger,6 T. Venkova,2 I. Yigitoglu,12 N. V. Zamfir,3,13 and O. Zeidan6 1Department of Physics, Istanbul University, Vezneciler, 34134, Istanbul, Turkey 2Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, BG-1784 Sofia, Bulgaria 3Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520, USA 4Department of Physics, University of Richmond, Richmond, Virginia 23173, USA 5Max-Planck-Institut fur Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany 6Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA 7Faculty of Physics, St. Kliment Ohridski University of Sofia, BG-1164 Sofia, Bulgaria 8Louisiana State University Department of Physics and Astronomy 202 Nicholson Hall, Tower Drive, Baton Rouge, Louisiana 70803-4001, USA 9Department of Physics, U.S. Naval Academy, Annapolis, Maryland 21402, USA 10Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA 11TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada 12Gaziosmanpasa University, Science Faculty, Turkey 13National Institute for Physics and Nuclear Engineering, Bucharest-Magurele, Romania (Received 14 July 2012; published 12 November 2012)

Excited low-spin, nonyrast states in {sup 170,172,174}Hf were populated in {beta}{sup +}/{epsilon} decay and studied through off-beam {gamma}-ray spectroscopy. New coincidence data allowed for a substantial revision of the level schemes of {sup 170,172}Hf and a confirmation of the level scheme of {sup 174}Hf. The Hf isotopes represent a unique situation in which a crossing of collective intrinsic excitations occurs, enhancing significantly the effects of mixing. Using branching ratios from excited 2{sup +} states, this mixing is followed and studied. The resulting mixing matrix elements are found to be {approx}30 keV - an order of magnitude larger than estimated previously for nearby nuclei. In the case of {sup 170}Hf, the 2{sub {beta}}{sup +} and 2{sub {gamma}}{sup +} level are shown to be completely mixed.

Studying the weak nuclear response, especially the Gamow-Teller (GT) transitions, of stable as well as unstable pf-shell nuclei, is one of the key issues in nuclear and astro-nuclear physics. We study the decay half-lives and the GT transitions starting from Tz = ±1 and ±2 mirror nuclei, respectively, by means of β decays and complementary hadronic (3 He , t) charge-exchange reactions. Under the assumption that isospin is a good quantum number, symmetry is expected for mirror nuclei and the GT transitions starting from the mirror nuclei. The half-lives and branching ratios and the measured strength distributions of GT transitions are compared and also combined for the understanding of the nuclear structure of pf-shell nuclei far-from-stability.

The $g$ factor of the ${2}_{1}^{+}$ state of $^{170}\mathrm{Hf}$ was measured by perturbed \ensuremath{\gamma}-\ensuremath{\gamma} angular correlation in a static external magnetic field. The result, $g({2}_{1}^{+})=0.28$(5), extends the systematics of $g$ factors of even-even Hf isotopes to $N=98$ and enables a better test of theoretical models. The $g({2}_{1}^{+})$ experimental values of these isotopes exhibit a remarkable constancy as a function of neutron number. This phenomenon, which was also observed for other isotopic chains in the Gd--W range, is explained in terms of a recently proposed empirical model.

High-spin states of {sup 191,193}Au and {sup 192}Pt have been populated in the {sup 186}W({sup 11}B, xn) and {sup 186}W({sup 11}B, p4n) reactions, respectively, at a beam energy of 68 MeV and their {gamma} decay was studied using the YRAST Ball detector array at the Wright Nuclear Structure Laboratory at Yale University. The level scheme of {sup 193}Au has been extended up to I{sup {pi}}=55/2{sup +}. New transitions were observed also in {sup 191}Au and {sup 192}Pt. Particle-plus-Triaxial-Rotor (PTR) and Total Routhian Surface (TRS) calculations were performed to determine the equilibrium deformations of the Au isotopes. The predictions for oblate deformations in these nuclei are in agreement with the experimental data. Development of nonaxial shapes is discussed within the framework of the PTR model.

Lifetimes of excited states in 128 Ce were measured using the recoil distance Doppler-shift (RDDS) and the Doppler-shift attenuation (DSAM) methods. The experiments were performed at the Wright Nuclear Structure Laboratory of Yale University. Excited states of 128 Ce were populated in the 100 Mo (32 Si ,4 n ) reaction at 120 MeV and the nuclear γ decay was measured with an array of eight Clover detectors positioned at forward and backward angles. The deduced yrast transition strengths together with the energies of the levels within the ground-state (gs) band of 128 Ce are in agreement with the predicted values for the X (5) critical point symmetry. Thus, we suggest 128 Ce as a benchmark X (5) nucleus in the mass A ≈ 130 region.

High-spin states of $^{187}\mathrm{Ir}$ have been populated in the $^{176}\mathrm{Yb}(^{15}\mathrm{N},4n)$ reaction and measured with the YRAST Ball spectrometer. The $\ensuremath{\pi}{h}_{9∕2}$ rotational band has been extended beyond the first alignment crossing, which was found at rotational frequency $\ensuremath{\hbar}{\ensuremath{\omega}}_{c}\ensuremath{\approx}0.39\phantom{\rule{0.3em}{0ex}}\text{MeV}$. Two different scenarios for describing this crossing are considered: the alignment of an ${h}_{9∕2}$ proton or ${i}_{13∕2}$ neutron pair and it is concluded that a proton band crossing is more likely. A systematic study of the rotational alignment crossings in the $\ensuremath{\pi}{h}_{9∕2}$ bands in the $N=104,106,108$ isotopes of $_{73}\mathrm{Ta},_{75}\mathrm{Re},_{77}\mathrm{Ir},$ and $_{79}\mathrm{Au}$ is presented.