Study of the threshold anomaly effect in the reaction $$^{7}$$Li+$$^{208}$$Pb at energies around the Coulomb barrier

Abstract

The elastic scattering in the reaction $$^{7}$$ 7 Li+$$^{208}$$ 208 Pb was investigated in the bombarding energy range from 25 to 39 MeV. The real and imaginary parts of the optical potential were analyzed by using a phenomenological potential. A dispersion relation analysis is presented in order to investigate the threshold anomaly effect. It is concluded that $$^{7}$$ 7 Li has an intermediate behavior between the tightly bound nuclei such as $$^{16}$$ 16 O and the loosely bound nuclei such as $$^{6}$$ 6 Li where the lack of the threshold anomaly is unambiguously observed. Reaction cross sections are also extracted from the elastic scattering data and its comparison with the ones of other systems has been performed to draw hints on the effect of the breakup channel.

Study of the threshold anomaly in the elastic scattering of d+$^{197}$Au

“…The average sensitivity radii obtained for the real and imaginary parts of the optical potential are 10.5 and 11.5 fm, respectively; then, the following value was taken for R S = 11.0 ± 0.5 fm. This figure is much greater than for 7 Li on 208 Pb, R S = 8.2 ± 0.4 fm [55], but smaller than for 9 Be on 197 Au, R S = 12.1 ± 0.2 fm [10]. These results suggest that some connection between the value of R S and the breakup threshold energy might exist.…”

“…This property of the optical potential is a consequence of the fact that elastic scattering only probes the surface of the projectile-target interaction reaction, giving rise to the concept of sensitivity radius R S [2,54]. As an alternative the usual parameters variation [2,55] for the determination of the sensitivity radius, the so called notch method was used [56]. This last method is somehow more intuitive since one analyzes the effect on the cross-section addressed by a localized perturbation on the radial form factor of the potential, as shown in Fig.…”

Trends in particle and nuclei identification techniques in nuclear physics experiments

“…6.2.4). As an example, these quantities, measured in coincidence with the light charged particles detected by the 250 bi-telescopes of 8π LP at LNL in the fusion-evaporation and other channels [50][51][52][53], allow to estimate the reaction cross sections, to obtain a better understanding of the dynamics of processes occurring in heavy-ion induced reactions. This TOF spectrometer is well suited for both stable beams, presently available at LNL and future radioactive ion beams [54] produced by SPES [55].…”

Dynamics of 7Li breakup and its influence on elastic scattering: a study of 7Li + 144Sm system*

“…Some systems induced by the WB 7 Li projectile [9][10][11]17] showed the presence of BTA at energies around V B , where the imaginary potential strength increaed instead of dropping to zero. Other systems induced by the 7 Li projectiles [12][13][14] showed the absence of the BTA.…”

“…The absence of TA at energies around V B was observed in many systems induced by the WB 6,7 Li projectiles, and this was introduced as a new anomaly called the breakup threshold anomaly (BTA) [8]. Although the BTA is well presented in various systems induced by 7 Li projectiles, among them 7 Li + 27 Al [9], 28 Si [10], 138 Ba [11], and other systems such as 7 Li + 59 Co [12], 80 Se [13], 134 Ba [7], and 208 Pb [14], revealed the occurrence of the usual TA. These controversial results related to the occurrence of the BTA in systems induced by 7 Li make it an active research area [15,16].…”