Exploring the emission barriers in hot nuclei

The reactions Si-30 + Er-170 and Si-29 + Er-170 have been studied by the pa rticle-gamma coincidence method. The first chance a-particle spectrum from the decay of the Pb-200 compound nucleus at 80 MeV excitation energy has be en obtained by using a subtraction technique. The emission barrier distribu tion has been extracted from the first chance spectrum, using the second de rivative analysis, commonly employed in sub-barrier fusion studies. The com parison with earlier systematics demonstrates that the alpha -particle emis sion barriers of the excited systems are lower than those observed in the i nverse (capture) reactions on ground state nuclei. (C) 2001 Elsevier Scienc e B.V. All rights reserved.