Projectile Fragmentation of 129 Xe at E Lab =790 A·mev

We have measured production yields and longitudinal momentum distributions of projectile-like fragments in the reaction 129 Xe + 27 Al at an energy of E lab =790 A·MeV. Production cross sections higher than expected from sys-tematics were observed for nuclei in the neutron-deficient tails of the isotopic distributions. A comparison with previously measured data from the fragmentation of 136 Xe ions shows that the production yields strongly depend on the neutron excess of the projectile with respect to the line of β-stability. The momentum distributions exhibit a dependence on the fragment neutron-to-proton ratio in isobaric chains, which was not expected from systematics so far. This can be interpreted by a higher excitation of the projectile during the formation of neutron-deficient fragments.