WAVE SELECTION AND LATERAL INSTABILITIES IN MIXED AUTOCATALYTIC SYSTEMS

Chemical systems with mixed quadratic and cubic autocatalytic feedback support simple reaction-diffusion fronts under suitable circumstances . If reactant and autocatalyst species have equal diffusivities, then from typical initial seedings, the system selects between two differen t types of fronts depending on the relative strengths of the two chann els. In terms of the parameter mu = k(q)/(k(q) + k(c)[A](0)) where k(q ,c) are the rate coefficient for the quadratic and cubic channels and [A](0) is the initial reactant concentration, then with mu>1/3, the sy stem selects a ''quadratic type'' front determined only by the quadrat ic channel, but for mu<1/3, the system adopts a ''cubic type'' front i n which both channel contribute. For pure cubic autocatalysis (mu=0) t hese fronts become geometrically unstable if the diffusivity of the re actant exceeds that of the autocatalyst. The present paper examines th e selection of wave type and wave velocity and the onset of lateral in stabilities of smooth waves for mixed autocatalytic systems for arbitr ary reactant and autocatalyst diffusivities. (C) 1997 American Institu te of Physics.