THEORY OF NUCLEATION FROM THE GAS-PHASE BY A SEQUENCE OF REVERSIBLE CHEMICAL-REACTIONS

A general theory is presented for the problem of condensed-phase parti cle nucleation from gas-phase precursors via a sequence of reversible chemical reactions, where no supersaturated vapor exists. We consider a system in which nucleation is initiated by the reaction between an ' 'initiating species'' and a ''growth species.'' Subsequent steps in cl uster growth involve reversible reactions between a cluster and the gr owth species, producing a larger cluster and a volatile byproduct, whi ch may be considered a ''suppressing species.'' Following the mathemat ical formalism of homogeneous nucleation theory, a steady-state nuclea tion rate is derived in the form of a summation over discrete cluster sizes. The resulting nucleation rate is linearly proportional to the p roduct of the concentrations of the initiating species and the growth species, while the ratio of the concentrations of the growth species t o the suppressing species, relative to a suitably defined equilibrium value, is seen to play a similar role as the vapor saturation ratio in homogeneous nucleation. (C) 1997 American Institute of Physics.