Shell and pairing effects in alpha-accompanied fission

Supposing that an $\alpha$ emitter remains an $\alpha$ emitter while it undergoes fission, the $\alpha$-particle formation probability on the surface of the fissioning system is computed (at different moments of spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ and thermal neutron fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$) in the point-$\alpha$-particle approximation and within the shell model, the Woods-Saxon nucleonic configurations being mixed through pairing forces. The variation with position on the surface is given. The results obtained afford a qualitative explanation of the experimental angular distribution (including polar emission) of $\alpha$ particles accompanying the fission process.

NUCLEAR STRUCTURE, FISSION ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}\mathrm{}\left(\mathrm{sf}\right)\mathrm{}$, ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}(n, f)$ accompanied by emission of $\alpha$ particles; computed preformation probability of $\alpha$ particles for different shapes of the fissioning nucleus between saddle and scission.