Light charged fragments from the reactions ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{51}$V at 35 MeV/nucleon and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C at 50 MeV/nucleon have been measured with a 4π array. Transverse collective motion is observed for all fragment types and increases in strength for the heavier fragments. The transverse momentum is qualitatively similar for the different impact parameters selected by the midrapidity charge. The global transverse momentum analysis includes corrections for correlations due to momentum conservation. The results are compared to those at higher energies to investigate whether the same or a new reaction phenomenon produces the collective motion. We outline some implications for the extraction of thermodynamic information from the kinetic energy of emitted fragments.

• Received 28 August 1989

DOI:https://doi.org/10.1103/PhysRevC.40.2592