[en] New sideband partners of the yrast bands built on the πh_11/2νh_11/2 configuration were identified in ₅₅Cs , ₅₇La , and ₆₁Pm N=75 isotones of ¹³⁴Pr . These bands form with ¹³⁴Pr unique doublet-band systematics suggesting a common basis. Aplanar solutions of 3D tilted axis cranking calculations for triaxial shapes define left- and right-handed chiral systems out of the three angular momenta provided by the valence particles and the core rotation, which leads to spontaneous chiral symmetry breaking and the doublet bands. Small energy differences between the doublet bands suggest collective chiral vibrations

[en] Excited states in ¹⁹⁶Au, populated in the ¹⁹⁶Pt(p,n) and (d,2n) reactions, were investigated by in-beam γ-ray and conversion-electron spectroscopy. Two only weakly connected level structures, built on the 2^- ground state (negative-parity level scheme) and on the 5⁺ isomer at 84.7 keV (positive-parity level scheme), are observed. The point of main effort of the present work was the investigation of the negative-parity level scheme in connection with its description within the framework of an extended supersymmetry. For this level scheme we observe 25 excited states up to an excitation energy of 500 keV, of which 23 had already been identified in a recent study of ¹⁹⁶Au by transfer reactions. From 500 to 800 keV we observe 28 additional levels compared to 20 levels observed in the transfer reactions. The excitation energies derived in the studies of the (p,n) compound reaction and the (p,d) transfer reaction agree within 1 keV, and the complementary information obtained from the two reactions led to improved spin determinations. The negative-parity level structure is compared with the predictions of the extended supersymmetry

[en] The g factors of the 4₁⁺ and 6₁⁺ states in ^144,148Nd, the 4₁⁺ state in ¹⁴⁶Nd and the 6₁⁺, 8₁⁺, and 10₁⁺ states in ¹⁵⁰Nd have been measured for the first time by projectile Coulomb excitation coupled to the transient field technique. The g factors of the 2₁⁺ states of ^{144,146,148,150}Nd have been remeasured with high precision. The data clearly indicate that, while ^148,150Nd are well described by collective excitations, the structure of the low lying levels in the lighter isotopes is dominated by the 2f_7/2 neutron configuration

[en] Subpicosecond lifetimes of states in shears band 1 in ¹⁹⁷Pb were measured by means of the recoil distance method employing Gammasphere and the New Yale Plunger Device. The extracted reduced matrix elements, B(M1) , show a clear sensitivity to the crossing of different shears configurations reflecting the closing and reopening of the shears blades. The energies and B(M1) values in the band crossing region are successfully described in the framework of the semiclassical model of the shears bands. The relevance of core rotation contributions are shown. The results point to the existence of shears states with an angular momentum coupling angle larger than 90^o

[en] The high-spin structure of ²⁰³Rn has been investigated using two separate reactions. γ-γ coincidences were measured for the ¹⁷⁴Yb(³⁴S,5n) reaction at a beam energy of 167 MeV using the YRAST Ball array at the Wright Nuclear Structure Laboratory at Yale University. The ¹⁶⁸Er(⁴⁰Ar,5n) reaction at an energy of 188 MeV was also employed. In this experiment γ rays were observed using the Gammasphere array in coincidence with the fragment mass analyzer at Argonne National Laboratory. The level scheme of ²⁰³Rn has been developed to spins of ∼41/2ℎ and excitation energies of ∼3 MeV. The high-spin decay is dominated by three sequences of γ rays, and the possible configurations are discussed

[en] Lifetimes in the neutron-rich nuclei ¹⁰⁴Mo, ¹¹⁰Ru, and ¹⁴⁴Ba were measured using the differential recoil distance method. The experiment was performed with a ²⁵²Cf fission source inside the New Yale Plunger Device. γ rays were detected by the SPEctrometer for Experiments with Doppler shifts at Yale (SPEEDY) while fission fragments with the appropriate kinematics were detected by an array of photocells

[en] We identify the J^π=2₃⁺ state of ⁹⁶Ru as the proton-neutron mixed-symmetry 2_ms⁺ state of this nucleus. This identification is based on the measurement of the transition strengths B(M1,2₃⁺→2₁⁺)=0.78(23) μ_N² and B(E2;2₃⁺→0₁⁺)=1.6(3) W.u. These transition strengths were obtained from the Coulomb excitation yield for the population of the 2₃⁺ state relative to the yield of the 2₁⁺ state with known E2 excitation strength. The Coulomb excitation was done in inverse kinematics using the reaction ^natC(⁹⁶Ru,⁹⁶Ru^{(small star, filled)}) at 280 MeV. This work demonstrates the accessibility of the isovector quadrupole excitation in the valence shell using experiments with an accelerated beam of the nuclei of interest

[en] High-spin states in the doubly odd N=75 nuclei ¹³⁶Pm and ¹³⁸Eu were populated following the ¹¹⁶Sn(²⁴Mg,p3n) and ¹⁰⁶Cd(³⁵Cl,2pn) reactions, respectively. A new ΔI=1 band is reported in ¹³⁸Eu and new data are presented for the recently reported band in ¹³⁶Pm. Polarization and angular correlation measurements have been performed to establish the relative spin and parity assignments for these bands. Both bands have been assigned the same πh_11/2(direct product)νh_11/2 structure as the yrast band and are suggested as candidates for chiral twin bands

[en] Here, the γ-ray strength function and level density in the quasi-continuum of ^151,153Sm have been measured using bismuth germanate shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow an extraction of the γ strength down to unprecedentedly low γ energies of ≈ 500 keV. For the first time an enhanced low-energy γ-ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well-known scissors resonance have been observed simultaneously for the same nucleus. Hauser-Feshbach calculations show that this strength enhancement at low γ energies could have an impact of 2 3 orders of magnitude on the (n, γ) reaction rates for r-process nucleosynthesis.

[en] We measured the ratio of the fission probabilities of ²³⁴U* relative to ²³⁶U* formed via an (α,α(prime)) direct reactions using the STARS array at the 88-inch cyclotron at the Lawrence Berkeley National Laboratory. This ratio has a shape similar to the ratio of neutron capture probabilities from ²³³U(n; f) and ²³⁵U(n; f), indicating the alpha reactions likely formed a compound nucleus. This result indicates that the ratios of fission exit channel probabilities for two actinide nuclei populated via (α, α(prime)) can be used to determine an unknown fission cross section relative to a known one. The validity of the External Surrogate Ratio Method (ESRM) is tested and the results support the conclusions of Burke et al. [1]