Precompound emission in low-energy heavy-ion interactions from recoil range and spin distributions of heavy residues: A new experimental method

Abstract

Recent investigations of heavy-ion reactions at low incident energies have indicated the presence of precompound emission component in considerable strength. In most cases the strength of the precompound component is estimated from the difference in forward-backward distributions of emitted light fast particles and also from the analysis of the measured excitation functions. This paper reports a new method of deciphering the relative contributions of compound and precompound components associated with fusion of $^{16}\mathrm{O}$ with $^{159}\mathrm{Tb},^{169}\mathrm{Tm}$, and $^{181}\mathrm{Ta}$ targets by measuring the recoil ranges of heavy residues in an absorbing medium along with the online measurement of the spin distributions in reaction residues produced in the fusion $^{16}\mathrm{O}$ beam with $^{159}\mathrm{Tb}$ and $^{169}\mathrm{Tm}$ targets. Analysis of recoil range and spin distributions of the residues shows two distinct linear momentum-transfer components corresponding to precompound and compound nucleus processes. The input angular momentum associated with precompound products is found to be relatively lower than that associated with compound nucleus process. The precompound components obtained from the present analysis are consistent with those obtained from the analysis of excitation functions.