Particle spectra from reversed kinematics: Powerful probes of hot rotating nuclei

Inclusive1H/4He emission has been studied for three reactions in “reversed kinematics”,40Ar/56Fe/86Kr (8.5MeV/u)+12C. The4He spectra include the heretofore unobserved region of low c.m. energies in the direction of the heavy reactant. A test of forward-backward symmetry is made for the hot-spot, moving source model; the data do not support the model. Effective emission barriers for4He evaporation are found to be within ∼10% of the corresponding fusion barriers, while for1H evaporation the emission barriers are more than 25% lower. It is possible that deformations predicted by the rotating liquid drop model can account for the4He evaporation spectra, but substantial change in the standard evaporation treatment is required to explain the spectra for1H.