J.J.M. Beenakker

Rotational relaxation in mixtures of hydrogen isotopes and noble gases: Part I. Mixtures with parahydrogen

Abstract In gaseous binary mixtures of parahydrogen with 3He, 4He, Ne, Ar, Kr, Xe and oH2 rotational-translational relaxation times have been measured at several temperatures between 77 and 170°K. In all cases a linear relationship was found between the inverse relaxation time and concentration.

The influence of a magnetic field on the transport properties of gases of polyatomic molecules;: Part I, Viscosity

Abstract This is the first of a series of three papers dealing with the influence of a magnetic field on the transport properties of polyatomic molecules. After a general introduction we will present measurements of the influence of a magnetic field on the viscosity of several gases at room temperature. A description is given of a capillary Wheatstone bridge with a relative resolution of 2·10−6 in the viscosity. Data are given on O2, NO, N2, CO, normal H2, para H2, normal D2, ortho D2, HD, CH4, CD4, CD4, CF4 and CO2. For most gases the relative change at saturation is of the order of 10−3, with the exception of H2 and D2 where the effects are about 10−5. A qualitative discussion of the shape and the position of the curves as a function of the ratio of magnetic field and pressure is given.

A survey of experimental data related to the non-spherical interaction for the hydrogen isotopes and their mixture with noble gases

Abstract A survey is given of experimental data related to the rotational degrees of freedom for the hydrogen isotopes and their mixtures with noble gases below 300 K. The results are, in as far as possible, expressed in terms of effective cross sections. The compilation includes experimental data on sound absorption, depolarized Rayleigh and Raman light scattering, flow birefringence, nuclear magnetic relaxation, viscosity, thermal conductivity and the magnetic field effect on transport properties.

The thermal conductivity of polar gases in a magnetic field

Measurements are reported of the change in the thermal conductivity coefficients ▵λ∥ and ▵λ⊥ of polar gases under the influence of a magnetic field at room temperature. Investigated are the linear molecules HCl, DCl, HCN, OCS and CO2 and the symmetric top molecules CH3F, CD3F, CH3CN, CHF3, NH3 and ND3. The results on the nonequilibrium polarizations WJ and W⊔JJ obtained from these experiment are expressed in terms of effective cross sections. With the present results the amount of data now available on certain effective cross sections has grown to an extent that justifies a systematic overview. Correlations are presented between the effective cross sections and various molecular properties such as the electric dipole moment and the moments of inertia.

Rotational relaxation of HD below 40 K

Abstract Sound absorption measurements are reported for the systems HD, HD-He and HD-Ne at a number of temperatures between 20.4 and 42.6 K. for HD the times for relaxation between the rotational and the translational degrees of freedom through collisions with HD and through collisions with He are derived. For HD-Ne the present method turns out to be inadequate to determine rotational relaxation times. For HD-HD collisions it is found that the collision number, Zrot, has a temperature - independent value of about 10, whereas for HD-He collisions Zrot is about 17.

A classical dynamics study of rotational relaxation in nitrogen gas

Rotational relaxation, related to the experimentally accessible volume viscosity, is described to the first order in the Sonine polynomial expansion of nonequilibrium distribution functions by the well known Wang Chang, Uhlenbeck, and De Boer expression. By a classical trajectory evaluation of a classical limit of this expression, using a recently proposed anisotropic inter-molecular potential for N2-N2, results are obtained for the rotational relaxation cross section. A corresponding expression including second order Sonine terms is also investigated. The second order results are found to differ significantly from the first order treatment (by about 18% at room temperature) and to agree very well with ultrasonic measurements over a temperature range from 77 K to 293 K.

Transverse momentum transport in viscous flow of diatomic gases in a magnetic field

Abstract It is prove experimentally that, in a magnetic field, transverse momentum transport occurs in viscous flow of diatomic molecules. The experimental results agree with theoretical calculations. The sign of the molecular gyromagnetic ratio can be determined.

Rotational relaxation in ortho hydrogen between 170 and 300 K

Abstract An apparatus for the preparation of enriched ortho hydrogen is described. Rotational relaxation times are reported for the J = 1 ⇄ 3 transition in ortho hydrogen at 170, 233, 269 and 293 K. A survey is given of the possibilities and limitations in the comparison of the experimental data with theory.

Viscosity and thermal conductivity of polar gases in an electric field

Abstract The influence of an electric field on the viscosity and thermal conductivity of gases of polar molecules has been investigated both theoretically and experimentally. The two different methods to solve the kinetic equation for polar symmetric top molecules, i.e. the perturbative method, employed by Mikhaǐlova and Maksimov, and the variational method, employed by Levi, McCourt and Tip, have both been refined. The improved methods now yield the same result: the field dependence of the electric effect is essentially the same as obtained by Mikhaǐlova and Maksimov whereas the terms contributing to the effect are essentially those given by Levi, McCourt and Tip. Measurements on the viscosity coefficient η 3 and the thermal conductivity coefficient λ″ are described. The hot-wire method which has been used for the thermal conductivity measurements is thoroughly discussed. The experimental results extend to the linear molecule NO, the oblate symmetric top molecules: NF 3 , CHF 3 , CHCl 3 , N(CH 3 ) 3 , the prolate symmetric top molecules: CH 3 F, CH 3 Br, CH 3 CN and the slightly asymmetric top molecules: CH 3 NH 2 , C 2 H 5 Cl, C 2 H 5 CN, CH 3 NO 2 . The data for η 3 are in direct agreement with the improved theory, taking one term into account. The behaviour of λ″ can also be explained on the basis of the improved theory, but generally two terms have to be taken into account, including one term due to non-invertible collisions. The cross sections derived from the η 3 data agree with the cross sections obtained from nonresonant absorption.

Rotational relaxation in mixtures of hydrogen isotopes and noble gases: Part II. Mixtures with orthodeuterium

In gaseous binary mixtures of orthodeuterium with 4He, Ne, Ar and pH2 rotational-translational relaxation times have been measured at temperatures between 30 and 90°K.