Evolution of the momentum distribution with mass loss in projectile fragmentation reactions

Background: Momentum distributions of fragmentation products as a function of fragment mass have been used to study the fragmentation mechanism. The parallel component of the momentum distribution has been well studied previously and modeled. The perpendicular component, however, is much less measured or understood.Purpose: Measure both components of the linear momentum of a wide range of fragmentation products and compare the widths of the momentum distributions to previous results and descriptions.Method: The parallel and perpendicular components of the momentum vector have been measured for projectile-like fragments produced in the reactions of ${}^{76}$Ge with ${}^{9}$Be and ${}^{197}\phantom{\rule{-0.16em}{0ex}}$Au at 130 MeV/nucleon in a magnetic spectrometer.Results: The measured parallel momentum distributions of all fragments follow established systematics. The perpendicular momentum distributions of fragments produced by fragmentation by the ${}^{197}\phantom{\rule{-0.16em}{0ex}}$Au target with masses near that of the projectile exhibit a clear peak near the momentum corresponding to the grazing angle that diminishes with decreasing fragment mass.Conclusions: The interplay between Coulomb and nuclear scattering can be used to describe results for the most peripheral collisions.