Projectile fragmentation of 129 Xe at E lab = 790 A MeV

We have measured production yields and longitudinal momentum distributions of projectilelike fragments in the reaction ${}^{129}$Xe+${}^{27}$Al at an energy of ${E}_{\mathrm{lab}}$=790$A$ MeV. Production cross sections higher than expected from systematics 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 $\ensuremath{\beta}$ 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.