  We show that ratios of light-particle energy spectra display scaling
properties that can be accu- rately described by effective local chemical
potentials. This demonstrates the equivalence of t/3He and n/p spectral ratios
and provides an essential test of theoretical predictions of isotopically
resolved light-particle spectra. In addition, this approach allows direct
comparisons of many theoretical n/p spectral ratios to experiments where
charged-particle spectra but not neutron spectra are accurately measured. Such
experiments may provide much more quantitative constraints on the density and
momentum dependence of the symmetry energy.
