Emission of boron fragments in reactions induced by ¹⁶O up to 25 MeV/amu

In this paper we study the emission of B fragments in the interaction of ¹⁶O ions with ⁵⁹Co and ⁹³Nb at incident energies varying from 6 to 25 MeV/amu. As in the case of other intermediate mass fragments (IMF) observed in the same reactions and in reactions induced by other light ions at comparable incident energies, the B spectra are dominated at forward angles by a component originating by break-up of ¹⁶O, which at the higher incident energies is found to fragment after a quite sizeable energy loss. Another mechanism, dominating at large emission angles, favours the emission of low energy fragments and is attributed to the coalescence of nucleons during the cascade of N-N interactions by means of which the excited nuclei produced in the primary two-ion interaction thermalize.