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Register a new userLinear Polarization Measurements for High-Spin States in 146Gd
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A {gamma}-ray linear polarization measurement has been performed to directly determine the parities for the levels in 146Gd nucleus. High-spin states in this nucleus were populated in a reaction 115In + 34S at 140 MeV incident energy. Linearly polarized {gamma} - rays emitted from oriented states were measured using a Compton polarimeter consisting of an array of 8 Compton-suppressed Clover detectors. Unambiguous assignments of the spin and parity have been made for most of the observed levels and changes made in the previously reported spin-parity assignments for a few levels. Shell model calculations performed with judicious truncation over the {pi}(gdsh) valence space interpret the structure of only the low-lying levels up to J{pi} = 19+ and 9-. N = 82 neutron-core breaking is found to be essential for high spin states with excitation energies Ex > 7 MeV.
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The $ E2/M1 $ multipole mixing ratio ($ delta $), reported by J. Gizon et al. Phys. Rev. C 17, 596 (1978), for 365 keV $ gamma $-transition in isotope[129]Ba is reevaluated and found altered. Experimentally determined angular distribution coefficients indicate a large E2 admixture in the 365 keV $ gamma $-ray. Indeed, it is found in better agreement with the reported linear polarization value for this $ gamma $-ray.
The structure of high-lying states in $^{22}$Ne has been studied using the $^{14}$C($^{12}$C,$alpha$)$^{22}$Ne reaction at E($^{12}$C)= 44 MeV. The spins were determined by measuring double ($alpha$,$alpha$) angular correlations. Selective population of the 9$^-$ and 11$^-$ states at E$_x$=20.1 and 20.7 MeV, respectively, identifies those states as the 9$^-$ and 11$^-$ members of the first $K^{pi}$ = 0$^-$ band, whose lower members were investigated by a method using inverse kinematics and a thick gas target. The spin and parity of four other new levels were determined to be 9$^-$ (21.5 MeV),12$^+$ (22.1 MeV),9$^-$ (25.0 MeV) and 8$^+$ (22.9 MeV). The two levels 9$^-$ and 12$^+$ may belong to the rotational doublets.
The isomeric and {beta} decays of the N = Z +2 nucleus 96Ag were investigated at NSCL. A cascade of {gamma}-ray transitions originating from the de-excitation of a {mu}s isomer was observed for the first time and was found in coincidence with two previously-known transitions with energies of 470 and 667 keV. The isomeric half-life was determined as 1.45(7) {mu}s, more precise than previously reported. The existence of a second, longer-lived {mu}s isomer, associated with a 743-keV transition, is also proposed here. Shell model results within the (p_{3/2}p_{1/2}f_{5/2}g_{9/2}) model space, using the jj44b interaction, reproduced level energies and isomeric decay half-lives reasonably well.
Linear polarization measurements have been performed for $gamma$-rays in $^{91}$Ru produced with the $^{58}$Ni($^{36}$Ar, $2p1n$$gamma$)$^{91}$Ru reaction at a beam energy of 111 MeV. The EXOGAM Ge clover array has been used to measure the $gamma$-$gamma$ coincidences, $gamma$-ray linear polarization and $gamma$-ray angular distributions. The polarization sensitivity of the EXOGAM clover detectors acting as Compton polarimeters has been determined in the energy range 0.3$-$1.3 MeV. Several transitions have been observed for the first time. Measurements of linear polarization and angular distribution have led to the firm assignments of spin differences and parity of high-spin states in $^{91}$Ru. More specifically, calculations using a semi-empirical shell model were performed to understand the structures of the first and second (21/2$^{+}$) and (17/2$^{+}$) levels. The results are in good agreement with the experimental data, supporting the interpretation of the non yrast (21/2$^{+}$) and (17/2$^{+}$) states in terms of the $J_{rm max}$ and $J_{rm max}-2$ members of the seniority-three $ u(g_{9/2})^{-3}$ multiplet.
Nuclides in the vicinity of 94Ag have been studied with the Penning trap mass spectrometer JYFLTRAP at the Ion-Guide Separator On-Line. The masses of the two-proton-decay daughter 92Rh and the beta-decay daughter 94Pd of the high-spin isomer in 94Ag have been measured, and the masses of 93Pd and 94Ag have been deduced. When combined with the data from the one-proton or two-proton-decay experiments, the results lead to contradictory mass excess values for the high-spin isomer in 94Ag, -46370(170) or -44970(100) keV, corresponding to excitation energies of 6960(400) or 8360(370) keV, respectively.
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