  One of the main open problems in the physics of Lambda-hypernuclei is the
lack of a sound theoretical interpretation of the large experimental values for
the ratio Gn/Gp=G(Lambda n -> nn)/G(Lambda p -> np). To approach the problem,
we have incorporated a one-meson-exchange model for the Lambda N -> nN
transition in finite nuclei in an intranuclear cascade code for the calculation
of single and double-coincidence nucleon distributions corresponding to the
non-mesonic weak decay of 5_Lambda-He and 12_Lambda-C. Due to the elimination
of interferences, two-nucleon coincidences are expected to give a cleaner
determination of Gn/Gp than single-nucleon observables. Single-nucleon
distributions are found to be less sensitive to variations of Gn/Gp than
double-coincidence spectra. The comparison of our results with preliminary KEK
coincidence data allows us to extract a Gn/Gp ratio for 5_Lambda-He of
0.39+-0.11 when multinucleon induced channels are omitted.
