Dust coagulation in equilibrium molecular gas

We study coagulation of dust particles immersed in equilibrium molecular gas. The dissipative grain interactions are modeled by a constant coefficient of restitution, while for the adhesive interactions the model of Johnson, Kendall and Roberts is applied. We formulate the Boltzmann-type master equation for the mass–velocity distribution function of aggregates and use the Kramers–Moyal expansion for the grain–gas collision integral. We derive coagulation equations and kinetic coefficients for these equations and analyze different regimes of the system evolution.