V. D. Borman

Molecular transport in subnanometer pores: zero-point energy, reduced dimensionality and quantum sieving

Abstract In microporous materials quantum effects in molecular adsorption and transport become of importance if the difference between pore diameter and the molecular hard core is no longer large compared to the de Broglie wavelength of radial motion. Two aspects are discussed: the freezing of the radial degrees of freedom resulting in a one dimensional gas and the situation where the zero-point energy overcompensates the attraction of the walls, creating an energy barrier at the entrance of the pores. In both cases the material can act as a quantum molecular sieve.

A study of the interaction between nonspherical molecules and a surface using the thermomagnetic effect in a Knudsen gas

The paper deals with the use of thermomagnetic effect in a Knudsen gas (i.e., the effect of the magnetic field on the heat flow between two surfaces) in studying nonspherical scattering of polyatomic molecules from a solid surface. The dependence of the effect on the field orientation has been experimentally investigated for the first time. As a result, it has become possible to establish the ranks of the tensors that determine the dependence of the scattering probability on the orientation of the angular momentum of a molecule. A new approach for constructing a theory of the effect has been proposed. This approach takes account of the arbitrary law of spherically symmetric scattering and examines the case of appreciable values of the nonsphericity parameters. From a comparison between the theoretical and experimental dependences of the heat flow on the field magnitude and orientation the expressions for the probability of inelastic nonspherical scattering of N2 and CO molecules by gold and platinum surfaces have been obtained.

The effect of a magnetic field on the Knudsen gas flow

Abstract The effect of a magnetic field on the Knudsen gas flow in a flat channel has been considered. The effect of the change of the channel resistance in the field is due to the polarization of molecules when they collide with the surface and to the destruction of this polarization in the magnetic field.

On kinetic thermomagnetic phenomena in polyatomic Knudsen gases

Abstract The thermomagnetic force, transverse heat flux and thermomagnetic pressure difference in a polyatomic Knudsen gas are discussed. The effect of a field on the transport phenomena in a Knudsen gas is considered to be associated with a nonspherical interaction of the molecules with the surface.

Effect of magnetic field on heat flow in a polyatomic gas in intermediate pressure range

The effect of a magnetic field, B, on heat flow in a gas in an intermediate pressure range has been studied. The ratio of the heat flow changes in the fields B ⊥ ▿T and B ‖ ▿T was found to change nonmonotonically with pressure in N2 and CO. With the decreasing pressure, a difference is observed between the dependence of heat flow on field orientation and the corresponding angular dependence in the limiting case Kn→0 (Kn = l/L, l is the mean free path, L is the geometric size). An expression has been obtained for the heat flow in a magnetic field for Kn ≲ 0.1 from the solution of an integral kinetic equation. In particular, it has been shown that the special features of the Senftleben-Beenakker effect observed with the decreasing pressure arise not only due to spherically symmetric molecule-surface interaction, but also to nonspherical scattering on walls.

Kinetic theory of rotating molecule interaction with a solid surface

A kinetic theory of interaction between molecules with rotational degrees of freedom and a solid surface for arbitrary ratios among the times of molecule rotation, flight through the region of surface forces, and relaxation of a molecular ensemble due to phonons has been developed. A kinetic equation for an ensemble of molecules residing in the field of surface forces has been derived from the equation for the one-particle distribution function of molecules by averaging it along the dynamical trajectories in the region of surface force action. A simple analytic expression for the probability of trapping a molecule with rotational degrees of freedom has been obtained. Experimental data on rotational cooling and rotational polarization of desorbed molecules are discussed.

Effect of the magnetic field on the activated processes at the surface of a magnetic solid in the vicinity of its Curie point

Abstract The external magnetic field has been shown to influence the kinetics of the activated process occurring at the surface of a magnetic solid as the temperature approaches its Curie point, T c . The dependence of the rate of such a process on temperature has been calculated on the basis of a combined description of the critical dynamics of a solid and the kinetics of the particles at its surface. It turned out that the rate of the process abnormally decreases when the spin of a particle is oriented parallel to the average magnetic moment of the solid and increases in the case of the antiparallel orientation as well as in the absence of a field.

Transport phenomena in a knudsen molecular gas in a magnetic field

We consider the behavior of a strongly rarefied (Knudsen) polyatomic gas between two surfaces that have different temperatures in a magnetic field. We show that in the magnetic field H there can arise a flux of gas and a heat flux along the surfaces (odd functions in H), and also normal and tangential forces on the walls.