Equilibrium distribution functions for plasma-molecular layers

ISSN： 1362-3028

Source： Molecular Physics, Vol.71, Iss.4, 1990-11, pp. : 721-757

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Abstract

The equilibrium distribution functions of free charged particles and those bound in molecules are calculated for a plasma-molecular system restricted by two parallel planes, taking into account all terms of the multipole expansion of the molecular fields. These distributions are used to find the inhomogeneous densities of free charged and neutral particles, the average molecular dipole moments and the total dipole moment of the system. In the case where particles approach the boundary of the system, the expressions obtained can diverge. The removal of the divergences is discussed. For a molecular subsystem modulated by rigidity coupled pairs of charged particles or an ensemble of harmonic atomic oscillators, the equilibrium distributions are investigated in the dipole approximation. The molecules contained in a purely molecular system or a plasmamolecular system with a hydrogen-like plasma subsystem are shown to have zero average dipole moments. For such systems the non-zero average dipole moments of molecules are calculated beyond the dipole approximation. The influence of the boundaries is shown to be similar to some effective field. If the media adjacent to the layer are similar, this effective field repels (attracts) the molecules from (to) the boundary planes if the dielectric permittivity of the molecular subsystem is greater (smaller) than the dielectric permittivity of the external media. The anisotropic equilibrium distributions of rigid dipoles are obtained and the dominant spatial orientations of dipoles are studied. The oscillator eigenfrequency shifts and the mean-square displacements of the oscillators are found for the system of harmonic atomic oscillators. Detailed numerical analyses are performed both for inhomogeneous spatial distributions of molecules and charged particles, and for anisotropic orientational distributions of rigid dipoles in molecular and plasma-molecular layers.