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Fission probes of sub-barrier fusion cross section enhancements and spin distribution broadening

T. MurakamiNuclear Physics Laboratory, University of Washington, Seattle, Washington 98195C. -C. SahmNuclear Physics Laboratory, University of Washington, Seattle, Washington 98195R. VandenboschNuclear Physics Laboratory, University of Washington, Seattle, Washington 98195D. D. LeachNuclear Physics Laboratory, University of Washington, Seattle, Washington 98195Anne E. RayNuclear Physics Laboratory, University of Washington, Seattle, Washington 98195Martin J. MurphyNuclear Physics Laboratory, University of Washington, Seattle, Washington 98195

1986en

ABI

Annotatsiya

The mean-square spin value of the compound nucleus $^{248}\mathrm{Cf}$ has been determined from fission fragment angular distributions for the $^{12}$C${+\mathrm{}}^{236}$U and $^{16}$O${+\mathrm{}}^{232}$Th reactions at sub-barrier bombarding energies. The anisotropy and hence the mean-square spin values are much larger than predicted by models which reproduce the cross section enhancement observed in the sub-barrier fusion excitation functions. A similar experiment with the spherical target $^{208}\mathrm{Pb}$ also leads to larger anisotropies and mean-square spin values than predicted by various fusion models, including an especially complete coupled channels calculation. Supplementary fragment-fragment coincidence experiments have been performed with the heavier targets to confirm that the observed fission is associated with full momentum transfer. The mass distribution for the $^{12}$C${+\mathrm{}}^{236}$U reaction has been measured at two angles and found to be independent of angle. This last result suggests that quasifission processes are not playing a significant role.

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Identifikatorlar

DOI: 10.1103/physrevc.34.1353

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