Quasi-stationary evolution of systems driven by particle evaporation

TL;DR

This paper investigates the quasi-stationary evolution of particle systems with evaporation, revealing how different collision dynamics influence energy distributions and the emergence of Michie-King-like profiles.

Contribution

It provides a numerical and theoretical analysis of how binary collision effectiveness affects the stationary states in evaporative systems.

Findings

Effective collisions lead to detailed balance and equilibrium-like states.

Weaker collision effectiveness results in Michie-King-like energy distributions.

Theoretical analysis accounts for nonhomogeneous confining potentials.

Abstract

We study the quasi-stationary evolution of systems where an energetic confinement is unable to completely retain their constituents. It is performed an extensive numerical study of a gas whose dynamics is driven by binary encounters and its particles are able to escape from the container when their kinetic energies overcome a given cutou Uc .We use a parametric family of differential cross sections in order to modify the effectiveness of this equilibration mechanism. It is verified that when the binary encounters favor an effective exploration of all accessible velocities, the quasi-stationary evolution is reached when the detailed balance is imposed for all those binary collisions which do not provoke particle evaporation. However, the weakening of this effectiveness leads to energy distribution functions which could be very well fitted by using a Michie-King-like profile. We perform a theoretical analysis, in the context of Hamiltonian systems driven by a strong chaotic dynamics and particle evaporation, in order to take into account the effect of the nonhomogeneous character of the confining potential.