Abstract
Recently it has been shown that the derivative non-linear Schrodinger equation, concerned with wave propagation in plasmas, can be associated with a modified Zakharov-Shabat inverse scattering problem. The authors produce an operator formula for the most general system of equations is solvable by this method and develop a perturbation theory capable of determining the variation in the scattering data to first order. They illustrate the theory by applying it to the derivative non-linear Schrodinger equation containing an additional perturbing harmonic forcing term, and consider the effect of this perturbation on an algebraic soliton.