Isospin Observables from Fragment Energy Spectra*

The energy spectra of light charged particles and intermediate mass fragments from $^{112}$Sn+$^{112}$Sn and $^{124}$Sn+$^{124}$Sn collisions at an incident energy of E/A=50 MeV have been measured with a large array of Silicon strip detectors. We used charged particle multiplicities detected in a near 4pi array to select data from the central collision region. We study isospin observables analogous to ratios of neutron and proton spectra, including double ratios and yield ratios of t/$^{3}$He and of asymmetries constructed from fragments with Z=3-8. Using the energy spectra, we can construct these observables as functions of kinetic energy and observe a large difference in the fragment observables if fragments contributing to sequential decays are included.