Isospin observables from fragment energy spectra

The energy spectra of light charged particles and intermediate mass fragments from 112Sn+112Sn and 124Sn+124Sn 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 an array with nearly 4π coverage to select data from the central collision events. We study isospin observables analogous to ratios of neutron and proton spectra, including double ratios and yield ratios of triton/3He and of asymmetries constructed from fragments with Z=3-8. Using the energy spectra, we can construct these observables as functions of kinetic energy. Most of the fragment asymmetry observables have a large sensitivity to sequential decays.