Time-scale of breakup of the halo nucleus 11Be

Abstract

We investigate the post-acceleration of the $^{10}$Be fragment in Coulomb breakup reaction of the halo nucleus $^{11}$Be, assuming that the excitation of the projectile is to states in the low energy continuum. The method used retains all finite-range effects associated with the interactions between the breakup fragments and can use realistic wave functions for the halo nuclei. We apply the method to compute the average momenta of the $^{10}$Be fragment at four different scattering angles following breakup of $^{11}$Be on a Au target at 42 MeV/nucleon beam energy. Our results, which are in qualitative agreement with recent precision experimental data, are consistent with the picture of no post-acceleration effect. The implication is that the breakup takes place on a time-scale long compared to the collision time.