Spin gap in a generalized one-dimensionalt-Jmodel

The existence of a spin gap is studied in a generalization of the one-dimensional t-J model. A frustrated next-nearest- neighbor exchange interaction, J', gives rise to a spin gap at half-filling that survives for small doping and arbitrary values of J. Regions of phase separation and divergent superconducting fluctuations are distorted but still present in the extended model.