NUCLEATION AND GROWTH OF A SOLID PHASE IN A GAS EXPANDING INTO VACUUM

Abstract

We study kinetics of homogeneous nucleation in over-saturated vapor expanding from a reservoir through a long channel into vacuum. Assuming adiabatic conditions for the gas, we derive an equation of state which accounts for the phase transformation of vapor into the condensed phase. To describe the growth rate of particles of the new phase gas kinetic theory is employed. We find the size-distribution of these particles, the temperature and flux velocity along the channel. Calculations are performed for the particular case of water vapor expanding to vacuum from its equilibrium state at the triple point. These conditions correspond presumably to the formation of the gas-dust plume, recently detected at Enceladus – the icy moon of Saturn. Our results, therefore, shed some light on this interesting astrophysical phenomenon.