Investigating the fission-like fragments in the $^{12}$C + $^{208}$Pb system at E$^{\star}$ $\approx$ 31.8--45.4 MeV

TL;DR

This study measures fission-like fragment cross-sections in the $^{12}$C + $^{208}$Pb reaction at moderate excitation energies, analyzing isotope distributions and dispersion parameters to understand fission processes and potential isotope production.

Contribution

It provides detailed measurements of fission fragment distributions and dispersion parameters at specific excitation energies, enhancing understanding of compound nucleus fission in this system.

Findings

Mass distribution fits Gaussian, indicating compound nucleus fission.

Mass variance increases linearly with excitation energy.

Populates medically relevant isotopes $^{99m}$Tc and $^{111}$In.

Abstract

In this work, the cross-sections of 25 fission-like fragments within the mass range 76$\leq$A$\leq$141, expected to be populated via fission of moderately excited compound nucleus produced as a result of complete and/or incomplete fusion in $^{12}$C+$^{208}$Pb reaction at E$_{\rm lab}$ = 81.9 and 75.8 MeV, have been measured using activation technique followed by offline $\gamma$-ray spectroscopy. The yields of different fission-like fragments have been analyzed to generate isotopic and isobaric yield distributions. The value of the mass dispersion parameter, $\sigma^2_A$, is found to be 2.93 and 2.65 for Antimony (Sb) isotope at excitation energy E$^{\star}$ = 45.4 and 39.6 MeV, and 1.24 for Indium (In) isotope at E$^{\star}$ = 45.4 MeV. The charge dispersion parameter $\sigma_Z$ for Sb is estimated to be 0.769 and 0.714 at E$^{\star}$ = 45.4 and 39.6 MeV, respectively. For In isotopes, the value of $\sigma_Z$ is estimated to be 0.430 at E$^{\star}$ = 45.4 MeV. The value of mass and charge dispersion parameters for Sb and In isotopes have been found to be in good agreement with the values reported in the literature for similar systems. The mass distribution of fission-like fragments is found to be fitted with a Gaussian function, except for a few data points, indicating their population via compound nucleus fission. Further, the mass variance ($\sigma^2_M$) displays linear increment with an increase in excitation energy. Two medically important isotopes, $^{99m}$Tc and $^{111}$In, are populated in this system, suggesting a potential formation route.