Study of the \(^{7}\)Li+\(^{154}\)Sm inelastic reaction using particle-\(\gamma \) coincidences

Abstract

The study of collectivity phenomena in atomic nuclei, such as nuclear deformation, provides essential information to characterize the nuclear potential in the different mass regions of the nuclear chart. The use of inelastic reactions in combination with particle-\(\gamma \) coincidences is a powerful experimental tool utilized to characterize near-ground excited states in reactions using deformed nuclei as targets and light-beam isotopes. This allows for the simultaneous study of both the states of nuclei in the beam and the target. The present work reports the first attempt to study the first excited states of the deformed \(^{154}\)Sm isotope by measuring the Differential Cross-Section of the inelastic excitation of the target system \(^{7}\) Li beam \(+\) \(^{154}\) Sm. The particle \(\gamma \)-ray coincidence technique has been used to study the \(^7\)Li + \(^{154}\)Sm inelastic reactions at 26 MeV beam energy. Charged particles were detected using an array of \(\Delta E-E\) phoswich detectors, while \(\gamma \)-ray radiation was registered using two arrays of LYSO(Ce) detectors. The results were analyzed using coupled-channel calculations with the FRESCO code of the inelastic cross-section for different nuclear potentials. The Differential Cross-Section for inelastic excitations of \(^{154}\)Sm of \(2^+\) (\(E^{\star }=0.082\) MeV), \(4^+\) (\(E^{\star }=0.267\) MeV), and \(6^+\) (\(E^{\star }=0.544\) MeV), as well as the \(1/2^-\) (\(E^{\star }=0.478\) MeV) state of the \(^7\)Li projectile is reported for the first time. Theoretical comparisons suggest that the \(0^+\rightarrow 4^+\) and \(0^+\rightarrow 6^+\) transitions of \(^{154}\) Sm are crucial to describe how these states are populated. In this work, the cross section of the inelastic scattering reaction \(^7\)Li\(+^{154}\)Sm at 26 MeV beam energy was studied and compared with coupled channel calculations using modified potentials to understand the influence of different coupling mechanisms. The analysis of \(^{154}\)Sm suggests that it should be considered a quantum rotor in which each excited state represents an addition of the angular momentum of \(l=2\hbar \). The experimental data also indicate that in addition to the ground state \(0^+\), the \(2^+\) (\(E^{\star }=0.082\) MeV), \(4^+\) (\(E^{\star }=0.267\) MeV), and \(6^+\) (\(E^{\star }=0.544\) MeV) states of the target nucleus should be added to the coupling scheme, as well as the ground state \(3/2^-\) and the \(1/2^-\) (\(E^{\star }=0.478\) MeV) of the projectile nucleus.