C. Maguire

Systematics of back angle 12C scattering — the 12C + 20Ne and 12C + 24Mg systems

Abstract The back angle scattering of 20 Ne and 24 Mg ions from 12 C display structured excitation functions and oscillatory angular distributions. These measurements bridge the gap between the previously studied 12 C + 16 O and 12 C + 28 Si systems.

g-factor measurements in 68Ge and evidence for higher multipole forces

The g-factors of the 4838 keV 81+ and 5050 keV 82+ states in 68Ge were measured by the transient field method to be 0.10+or-0.04 and -0.28+or-0.14, respectively, relative to a value of 0.4 for that of the 61+ level. The first theoretical description of the three 8+ levels in 68Ge, consistent with the experimental data on the backbending of I, B(E2) and g-factors, was obtained in a two-quasiparticle-plus-interacting-boson model. The inclusion of the generally neglected multipole forces higher than quadrupole was required.

Isometric trapping following Coulomb excitation of high spin states in 178Hf

Abstract Coulomb excitation of states in 178, 180 Hf has been observed to 16 + and 12 + , respectively, with Kr and Xe ions. A strong up bend in the moment of inertia above the 12 + level is seen in 178 Hf and is well reproduced by cranked shell model calculations. For the first time in Coulomb excitation, population of the lowest K π = 8 - isomer in 178 Hf was observed.

High-spin states and band structure inBr76

High-spin states of /sup 76/Br have been investigated through observations of ..gamma.. rays produced in the /sup 66/Zn(/sup 12/C,pn) reaction by bombarding an enriched /sup 66/Zn target with 38.0-MeV /sup 12/C ions. Measurements were made of ..gamma..-ray singles and ..gamma..-..gamma.. coincidence spectra, ..gamma..-ray angular distributions, and ..gamma..-ray linear polarizations. Level energies, decay modes, spins and parities, ..gamma..-ray branching ratios, and ..gamma..-ray radiative admixtures were deduced. There is evidence for a strongly excited ..delta..J = 1 quasirotational band.

Fusion evaporation-residue cross sections for sup 28 Si+ sup 40 Ca at E ( sup 28 Si)=309, 397, and 452 MeV

Velocity distributions of mass-identified evaporation residues produced in the {sup 28}Si+{sup 40}Ca reaction have been measured at bombarding energies of 309, 397, and 452 MeV using time-of-flight techniques. These distributions were used to identify evaporation residues and to separate the complete-fusion and incomplete-fusion components. Angular distributions and upper limits for the total evaporation-residue and complete-fusion evaporation-residue cross sections were extracted at all three bombarding energies. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with earlier measurements and the predictions of existing models. The ratios of the complete-fusion evaporation-residue cross section to the total evaporation-residue cross section, along with those measured for the {sup 28}Si+{sup 12}C and {sup 28}Si+{sup 28}Si systems at the same energies, support the entrance-channel mass-asymmetry dependence of the incomplete-fusion evaporation-residue process reported earlier.

Fusion-evaporation cross sections for sup 24 Mg+ sup 24 Mg at 5 lt E sub lab lt 9 MeV/nucleon

The evaporation residue cross sections for the fusion of the {sup 24}Mg+{sup 24}Mg system have been obtained at laboratory energies of 111, 160, and 206 MeV. Angular distributions of the evaporation residues were measured and used to determine the cross sections. These cross sections decrease at the higher energies, characteristic of a limiting angular momentum. Results are compared with the predictions of fusion-evaporation models and to the systematics known from other light heavy-ion systems. Evidence is presented for a contribution from incomplete fusion and for a possible contribution from the evaporation of ejectiles heavier than {alpha} particles to the fusion-evaporation cross section at 206 MeV.