ISSN:
1434-601X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The cross sections for production of evaporation residues (σ er) and for fusion-fission (σ ff) have been measured for40Ar+144, 148, 154Sm at sub-barrier energies by observation of x-ray emission from radioactive products and by direct,ΔE−E identification of fission fragments, respectively. These isotopes span the transition region from spherical (144Sm) to strongly deformed (154Sm) equilibrium shapes. The cross section for fusion,σ fus=σ er+σ ff, is found to vary markedly at low energies with the isotope number and, hence, with the quadrupole collectivity of the target. The thresholds for fusion of148Sm and144Sm are, respectively, ∼3.5 MeV and ∼7 MeV (c.m.) higher than for fusion with154Sm. These differences and the energy dependence of the fusion cross sections are discussed in terms of the effect of nuclear deformation on heavy-ion fusion. A comparative analysis of results for16O+Sm and40Ar+Sm in terms of static deformation indicates thatσ fus for the Ar+Sm system at very low energies is enhanced relative to the prediction for a one-dimensional barrier based on a fit toσ fus for16O+Sm. This may be an indication that additional degrees of freedom (such as formation of a neck or fragment elongation) may be important for fusion with the larger projectile. At energies above the fusion barrier, values ofσ fus for144, 148Sm are nearly equal, but are significantly smaller than for154Sm. This is in contrast to the results of previous experiments with16O projectiles in whichσ fus (16O+148Sm) andσ fus (16O+154Sm) were nearly equal above the barrier. These differences, observed for144, 148Sm and154Sm at energies above the barrier may reflect a new mechanism which is not encompassed by a static theory.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01412207
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