New Mechanism ofα-Particle Production in Heavy-Ion-Induced Fission

Detailed studies have been made of the multiplicity, energy, and angular distributions of $\alpha$ particles emitted in coincidence with fission fragments from the ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ + ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ ($E_{\mathrm{lab}}=465\mathrm{}$ MeV) reaction. Approximately 90% of the $\alpha$ particles are evaporated from the two fully accelerated fission fragments. The remaining $\alpha$ particles have a strongly enhanced emission probability in the direction perpendicular to the scission axis, suggesting the contact or neck region between the fragments as the source of these particles.