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n_TOF Collaboration(Karadimos, D. et al), Domingo-Pardo, C., & Tain, J. L. (2014). Neutron-induced fission cross section of U-234 measured at the CERN n_TOF facility. Phys. Rev. C, 89(4), 044606–11pp.
Abstract: The neutron-induced fission cross section of U-234 has been measured at the CERN nTOF facility relative to the standard fission cross section of U-235 from 20 keV to 1.4 MeV and of U-238 from 1.4 to 200 MeV. A fast ionization chamber (FIC) was used as a fission fragment detector with a detection efficiency of no less than 97%. The high instantaneous flux and the low background characterizing the nTOF facility resulted in wide-energy-range data (0.02 to 200 MeV), with high energy resolution, high statistics, and systematic uncertainties bellow 3%. Previous investigations around the energy of the fission threshold revealed structures attributed to beta-vibrational levels, which have been confirmed by the present measurements. Theoretical calculations have been performed, employing the TALYS code with model parameters tuned to fairly reproduce the experimental data.
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Moradi, F. G. et al, & Huyuk, T. (2014). Spectroscopy of the neutron-deficient N=50 nucleus Rh-95. Phys. Rev. C, 89(4), 044310–8pp.
Abstract: The neutron-deficient semimagic (neutron number N = 50) Rh-95 nucleus has been produced at high spins using the projectile-target system Ca-40 + Ni-58 at 125 MeV beam energy. The gamma-decays of levels populated by the 3p fusion evaporation reaction channel were studied using gamma-gamma coincidences, and 20 new gamma-ray transitions involving 15 new positive-and negative-parity states were observed. Spin and parity for many of the excited states were firmly deduced for the first time using the combined directional angular correlation and direction-polarization techniques. The observed structures are discussed within the framework of large-scale shell model calculations. E1 transition strengths were deduced and used together with the results of the shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.
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Morales, A. I. et al, Gadea, A., & Algora, A. (2014). beta-decay studies of neutron-rich Tl, Pb, and Bi isotopes. Phys. Rev. C, 89(1), 014324–13pp.
Abstract: The fragmentation of relativistic uranium projectiles has been exploited at the Gesellschaft fur Schwerionenforschung laboratory to investigate the beta decay of neutron-rich nuclei just beyond Pb-208. This paper reports on beta-delayed gamma decays of Tl211-213, Pb-215, and Bi215-219 de-exciting states in the daughters Pb211-213, Bi-215, and Po215-219. The resulting partial level schemes, proposed with the help of systematics and shell-model calculations, are presented. The role of allowed Gamow-Teller and first-forbidden beta transitions in this mass region is discussed.
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Aydin, S. et al, Gadea, A., & Huyuk, T. (2014). High-spin level structure of S-35. Phys. Rev. C, 89(1), 014310–9pp.
Abstract: The nucleus S-35 has been studied by in-beam gamma-ray spectroscopy using the Mg-24(N-14,3p) fusion-evaporation reaction at E-lab = 40 MeV. A level scheme extended up to J(pi) = 17/2(+) at 8023 keV and J(pi) = 13/2(-) at 6352 keV has been established. Lifetimes of six excited states have been determined by applying the Doppler shift attenuation method. The experimental data have been compared with the results of large-scale shell model calculations performed using different effective interactions and model spaces allowing particle-hole excitations across the N = Z = 20 shell gap.
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Ghazi Moradi, F. et al, & Huyuk, T. (2014). Character of particle-hole excitations in Ru-94 deduced from gamma-ray angular correlation and linear polarization measurements. Phys. Rev. C, 89(1), 014301–9pp.
Abstract: Linear polarization and angular correlations of gamma-rays depopulating excited states in the neutron-deficient nucleus Ru-94(44)50 have been measured, enabling firm spin-parity assignments for several excited states in this nucleus. The deduced multipolarities of strong transitions in the yrast structure were found to be mostly of stretched M1, E1, and E2 types and, in most cases, in agreement with previous tentative assignments. The deduced multipolarity of the 1869 keV and the connecting 257 and 1641 keV transitions indicates that the state at 6358 keV excitation energy has spin parity 12(1)(-) rather than 12(3)(+) as proposed in previous works. The presence of a 12(1)(-) state is interpreted within the framework of large-scale shell-model calculations as a pure proton-hole state dominated by the pi(p(1/2)(-1)circle times g(9/2)(-5)) and pi(p(3/2)(-1) g(9/2)(-5)) configurations. A new positive-parity state is observed at 6103 keV and is tentatively assigned as 12(2)(+). The 14(1)(-) state proposed earlier is reassigned as 13(4)(-) and is interpreted as being dominated by neutron particle-hole core excitations. The strengths of several E1 transitions have been measured and are found to provide a signature of core-excited configurations.
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