Effects of the valence neutron of the lithium isotopes in ^6,7,8Li+²⁰⁸Pb systems

¹ Department of Physics, Dong-Eui University, Busan 614-714, Korea
² Department of Radiological Science, Kangwon National University, Samcheok 245-711, Korea

^a e-mail: wyso@kangwon.ac.kr

Abstract

Using the measured experimental data for ^6,7,8Li+²⁰⁸Pb system, we investigated the relation between the interaction distance and the lowest threshold separation energy of the projectiles. Although ⁶Li can be considered more weakly bound projectile than ⁸Li, the lithium isotope with the largest interaction distance is not ⁶Li but ⁸Li. Also, we can infer that the difference of the semiexperimental direct reaction (DR) cross sections and the total breakup / transfer reaction cross sections comes from α and ⁷Li capture. Finally, the barrier height, VB , of ⁸Li + ²⁰⁸Pb system compared with ⁷Li + ²⁰⁸Pb system are reduced about 3MeV. This is the rise of flux from exp the elastic into the reaction channel, which tends to enhance σ_R^exp . As a result, we can deduce that the valence neutron play a role as the lowering of the barrier height.