Spin distribution of the compound nucleus formed by sup 16 O+ sup 154 Sm

• Published in: Physical review. C, Nuclear physics Nuclear physics, 1991-02, Vol.43:2
• Main Authors: Gil, S., Vandenbosch, R., Charlop, A., Garcriaaa, A., Leach, D.D., Luke, S.J., Kailas, S.
• Format: Article
• Language: English
• Subjects: 651820 - Nuclear Properties & Reactions, A=150-189, Experimental; 653001 - Nuclear Theory- Nuclear Structure, Moments, Spin, & Models; ALPHA REACTIONS; ANGULAR DISTRIBUTION; ANGULAR MOMENTUM; CHARGED-PARTICLE REACTIONS; COINCIDENCE SPECTROMETRY; COMPOUND-NUCLEUS REACTIONS; CROSS SECTIONS; DEFORMATION; DISTRIBUTION; ELECTROMAGNETIC RADIATION; ENERGY DEPENDENCE; ENERGY LEVELS; ENERGY RANGE; ERBIUM 166 TARGET; ERBIUM 167 TARGET; EVAPORATION MODEL; GAMMA RADIATION; HEAVY ION REACTIONS; HELIUM 3 REACTIONS; IONIZING RADIATIONS; MATHEMATICAL MODELS; MEV RANGE; MEV RANGE 10-100; MULTIPLICITY; NUCLEAR DEFORMATION; NUCLEAR MODELS; NUCLEAR PHYSICS AND RADIATION PHYSICS; NUCLEAR REACTIONS; OXYGEN 16 REACTIONS; PARTICLE PROPERTIES; RADIATIONS; SAMARIUM 154 TARGET; SPIN; STATISTICAL MODELS; TARGETS; TIME-OF-FLIGHT METHOD
• ISSN: 0556-2813; 1089-490X
• DOI: 10.1103/PhysRevC.43.701

Gamma-ray multiplicities for the {sup 16}O+{sup 154}Sm system have been determined using two different coincidence techniques. Fusion events are tagged either by observation of low-lying gamma transitions in the evaporation residues or by direct detection of the residues exploiting an electrostatic deflector and time-of-flight identification. The gamma-ray tagging measurements have been made with higher sensitivity than previously, allowing us to include the contribution of the 3{ital n} channel. The contribution of this channel modifies the conclusions made before in regard to the spin distribution of the compound nucleus produced at near-barrier energies. The procedure for conversion of gamma-ray multiplicities to mean spin values has been calibrated by measuring gamma-ray multiplicities and fusion cross sections for the {sup 4}He+{sup 166}Er and {sup 3}He+{sup 167}Er reactions that lead to the same compound nucleus as {sup 16}O+{sup 154}Sm, at bombarding energies that span the same region of excitation energies and spin. The use of an electrostatic deflector enables an inclusive tag on all evaporation residues, and has sufficient sensitivity to enable measurements at a lower energy than is possible with gamma-ray tagging techniques. The energy dependence of the mean spin deduced from gamma-ray multiplicity measurements is in qualitative agreement with model calculations which include the effects of the static and dynamical deformations of the target nucleus. There is, however, a tendency for the calculations to underestimate somewhat the mean spin near and below the barrier.