Dominance of nuclear processes in the dissociation of 8B

We study the break-up of B-8 in collisions with heavy-ions. The process is described in terms of inelastic excitations leading to states in the continuum. The effects of the nuclear and Coulomb fields induced by the reaction partner are included on the same footing in the microscopic construction of the transition matrix elements. At variance with previous findings, the contribution of the nuclear component is found to be comparable to - and even larger than - that of the Coulomb one. Because of the weak binding energy of( 8)B the nuclear couplings associated with inelastic excitation to low-lying states in the continuum extend to unusually large distances, As a consequence, the interplay between nuclear and Coulomb excitation processes differs significantly from the situation encountered in reactions involving systems close to the stability line. In particular, nuclear excitation is found to remain predominant at energies well below the Coulomb barrier. (C) 1998 Elsevier Science B.V.