19 research outputs found
5He ternary fission yields of 252Cf and 235U(n,f)
The relative 4He and 5He ternary fission yields were determined from a careful analysis of the energy distribution of α spectra from a new measurement with a 252Cf source and from published data on 252Cf and 235U(n,f). The kinetic energies of the 5He and 4He ternary particles were found to be approximately 11 and 16 MeV, respectively. 5He particles contribute 10-20% to the total alpha yield with the remainder originating from 4He accompanied fission
First evidence for triaxial superdeformation in 168Hf
Three superdeformed (SD) bands have been found in 168Hf. Lifetime measurements revealed a large quadrupole moment, Qt ∼ 11.4 eb, for the strongest band (TSD1). Theoretical calculations using the Ultimate Cranker code predict high-spin SD minima (ε2 ∼ 0.43) with stable triaxial deformations of γ ∼ +20° and γ ∼ -15°. The measured Qt value suggests that band TSD1 corresponds, most likely, to a deformation with a positive γvalue. This constitutes the first evidence for triaxial superdeformation in an even proton system
Identification of 181Hg and shape coexistence in odd-A Hg isotopes
In-beam γ-ray transitions in 181Hg, the lightest odd-A Hg isotope known thus far, have been identified from fragment mass-γ and γ-γ coincidence measurements. Five prolate deformed rotational bands were placed in the level scheme. A decoupled band built on the strongly prolate deformed 1/2-[521] ground state was observed up to 29/2-. A 5/2-[512] configuration is suggested for a pair of strongly coupled bands displaying no signature splitting. The other two bands are also signature partner bands. They are populated with the largest intensity and exhibit splitting. They have been associated with the mixed neutron i13/2 orbitals and are proposed to decay to an i13/2 isomeric state associated with an oblate state
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Gammasphere software development
Activities of the nuclear physics group are described. Progress was made in organizing the Gammasphere Software Working Group, establishing a nuclear computing facility, participating in software development at Lawrence Berkeley, developing a common data file format, and adapting the ORNL UPAK software to run at Gammasphere. A universal histogram object was developed that defines a file format and provides for an objective-oriented programming model. An automated liquid nitrogen fill system was developed for Gammasphere (110 Ge detectors comprise the sphere)
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High spin states and the competition of spherical and strongly deformed shapes in the A = 70 to 80 region
A wide variety of collective band structures are seen in Ge to Sr nuclei to make this an important new testing ground for nuclear models. These include bands built on coexisting and competing near-spherical and deformed shapes, ..gamma.. vibrational bands and multiple positive and negative parity bands. Ground state bands in Ge and Kr but not /sup 78/ /sup 80/Sr are crossed at the 8/sup +/ to 12/sup +/ levels. Gaps in the Nilsson levels for both N and Z = 38 at large deformation lead to large ground state deformation in Kr and Sr around N = 38. The crossing of rotation aligned bands based on (g/sub 9/2/)/sup 2/ configuration are correlated with the ground state deformations. A second high spin crossing is seen in /sup 74/Kr. Measured g factors in /sup 68/Ge yield a two-quasineutron structure for the 8/sub 2//sup +/ state. 30 references