Investigation of the threshold anomaly for theLi7+Tb159system

Abstract

Elastic-scattering angular distributions were measured for the $^{7}\mathrm{Li}+^{159}\mathrm{Tb}$ system at various energies; namely, 24, 26, 28, 30, 35, 40, and 44 MeV. The optical-model analysis was performed to investigate the energy dependence of real and imaginary potentials, employing a Woods--Saxon form of potential. The dispersion-relation analysis were also carried out to check the consistency of real and imaginary parts of the potentials. The energy dependence of real and imaginary potentials does not follow the trend of conventional threshold anomaly but rather represents unusual behavior of the increase of imaginary part of the potential and corresponding decrease in real part of the potential near the Coulomb barrier energy. The effect of breakup coupling on elastic-scattering angular distributions was studied by a continuum-discretized coupled-channels (CDCC) calculation. The behavior of dynamic polarization potentials obtained due to the breakup coupling is discussed. The total reaction cross sections for the present and various other systems are also compared involving $^{7}\mathrm{Li}$ projectile on different target nuclei in the mass range $A=16$ to 232.