Crossing of shears bands in 197Pb: B(M1) values and semiclassical description

Subpicosecond lifetimes of states in shears band 1 in 97Pb 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°

Measurement of conversion coefficients in normal and triaxial strongly deformed bands in Lu167

Internal conversion coefficients have been measured for transitions in both normal deformed and triaxial strongly deformed bands in Lu167 using the Gammasphere and ICE Ball spectrometers. The results for all in-band transitions are consistent with E2 multipolarity. Upper limits are determined for the internal conversion coefficients for linking transitions between TSD Band 2 and TSD Band 1, the nw=1 and nw=0 wobbling bands, respectively

Possible origins of macroscopic left-right asymmetry in organisms

I consider the microscopic mechanisms by which a particular left-right (L/R) asymmetry is generated at the organism level from the microscopic handedness of cytoskeletal molecules. In light of a fundamental symmetry principle, the typical pattern-formation mechanisms of diffusion plus regulation cannot implement the "right-hand rule"; at the microscopic level, the cell's cytoskeleton of chiral filaments seems always to be involved, usually in collective states driven by polymerization forces or molecular motors. It seems particularly easy for handedness to emerge in a shear or rotation in the background of an effectively two-dimensional system, such as the cell membrane or a layer of cells, as this requires no pre-existing axis apart from the layer normal. I detail a scenario involving actin/myosin layers in snails and in C. elegans, and also one about the microtubule layer in plant cells. I also survey the other examples that I am aware of, such as the emergence of handedness such as the emergence of handedness in neurons, in eukaryote cell motility, and in non-flagellated bacteria.Comment: 42 pages, 6 figures, resubmitted to J. Stat. Phys. special issue. Major rewrite, rearranged sections/subsections, new Fig 3 + 6, new physics in Sec 2.4 and 3.4.1, added Sec 5 and subsections of Sec

Proton and neutron excitations in superdeformed Tb150

Two new superdeformed (SD) bands have been observed in Tb150 using the reaction P31+124Sn and the GAMMASPHERE detector array. These new bands are interpreted as being excited SD configurations involving a proton and a neutron particle-hole excitation, respectively. The configurations are discussed in terms of the occupancy of high-N intruder orbitals. These data are used to provide information on (i) the contribution to the dynamic moments of inertia due to the occupation of specific orbitals, (ii) the deformation driving effects of the particle-hole states, and (iii) the consequences of these effects on pairing and band-crossings

Recoil-gated plunger lifetime measurements in 188Pb

Electromagnetic transition probabilities were measured using the recoil distance Doppler-shift technique and the 40Ca(152Sm,4n) 188Pb reaction at a beam energy of 805 MeV to investigate shape coexistence in 188Pb. For the first time, a plunger was combined with Gammasphere and the Argonne Fragment Mass Analyzer. It was possible to measure the lifetimes of two states in the prolate band of 188Pb and, thus, provide for the first time evidence for the collectivity of this band. A three-level mixing calculation revealed that the first 2+ state is predominantly of prolate character

New results on fission cross sections in actinide nuclei using the surrogate ratio method and on conversion coefficients in triaxial strongly deformed bands in167Lu from ice ball and gammasphere

The surrogate ratio technique is described. New results for neutron induced fission cross sections on actinide nuclei, obtained using this technique are presented. The results benchmark the surrogate ratio technique and indicate that the method is accurate to within 5% over a wide energy range. New results for internal conversion coefficients in triaxial strongly deformed bands in 167Lu are also presented

Investigation of negative-parity states in Dy 156: Search for evidence of tetrahedral symmetry

An experiment populating low/medium-spin states in Dy156 was performed to investigate the possibility of tetrahedral symmetry in this nucleus. In particular, focus was placed on the low-spin, negative-parity states since recent theoretical studies suggest that these may be good candidates for this high-rank symmetry. The states were produced in the Nd148(C12,4n) reaction and the Gammasphere array was utilized to detect the emitted γ rays. B(E2)/B(E1) ratios of transition probabilities from the low-spin, negative-parity bands were determined and used to interpret whether these structures are best associated with tetrahedral symmetry or, as previously assigned, to octupole vibrations. In addition, several other negative-parity structures were observed to higher spin and two new sequences were established

Triaxiality near the 110Ru ground state from Coulomb excitation

A multi-step Coulomb excitation measurement with the GRETINA and CHICO2 detector arrays was carried out with a 430-MeV beam of the neutron-rich 110Ru (t1/2=12 s) isotope produced at the CARIBU facility. This represents the first successful measurement following the post-acceleration of an unstable isotope of a refractory element. The reduced transition probabilities obtained for levels near the ground state provide strong evidence for a triaxial shape; a conclusion confirmed by comparisons with the results of beyond-mean-field and triaxial rotor model calculations