In 36Ar + 27A1 reactions at bombarding energies E/A from 55 to 95 MeV, the mass and excitation energy of the quasi-projectile have been reconstructed at all impact parameters. Up to excitation energies E*/A of ∼ 5-6 MeV, the mean kinetic energies of Z = 1 to Z = 9 fragments are in agreement with values predicted by sequential statistical decay. Above, a collective expansion energy is needed that grows with E*/A, reaching 1 to 2.2 MeV/u, depending on the de-excitation process, at E*/A ∼ 10 MeV. It decreases with the fragment charge. The dominant role of excitation energy supports the scenario of thermal expansion.
- Deduced quasi-projectile mass, excitation energy, thermal expansion evidence
- Measured fragment kinetic energy and charges with 4π-array
- Nuclear reactions al(ar, x), e = 55-95 mev/nucleon