Collision induced microwave absorption is reported in pure N2, CO2, and H Z in the region of 2.3 cm-'. For N 2 the results are taken at temperatures ranging from 208 to 333 K and at densities ranging from 50 to 300 amagat. The parts of the loss factor which are proportional to the square and the cube of the density are found to depend respectively on T-1."*o.12 and T-2.56'0.44. These results are well explained by the theory which relates the virial coefficients and relaxation times to the loss factor. Both the two and three body relaxation times, r 2 and r 3 follow very closely a T-0.5 dependence. The ratio of r2/r3 is found to be 0.83. For C 0 2 the results are taken a t temperatures ranging from 273 to 363 K and at densities ranging from 8 to 80 amagat. The parts of the loss factor which are proportional to the square and cube of the density depend respectively on T-3.08'0.05 and T-5.54'0.59 .'These results together with existing infrared results show that r 2 is nearly proportional to T-0.5 and the ratio r2/r3 is 0.91 at 296 K. An initial measurement is reported for collision induced absorption in Hz. The results for all three gases have been compared to previously reported results in the low frequency region. L'absorption micro-ondes induite par collisions est observee dans N2, CO,, et H Z dans la region de 2.3 cm-'. Pour N 2 les resultats sont obtenus pour des temperatures allant de 208 a 333 K et pour des densites de 50 a 300 amagat. Les composantes du facteur de perte qui sont proportionnelles au carre et au cube de la densite dependent de la temperature selon T-1.55'o.12 et T-2.56'0.44 respectivement. Ces resultats s'expliquent bien par la theorie qui relie les coefficients viriels et les temps de relaxation au facteur de perte. Les temps de relaxation a deux et a trois corps, r 2 et r3 suivent tres precisement la loi en T-o.5. On trouve le rapport r2/r3 egal a 0.83. Pour C 0 2 les resultats sont obtenus pour des temperatures de 273 a 363 K et des densites de 8 a 80 amagat. Les composantes du facteur de perte qui sont proportionnelles au carre et au cube de la densite dependent de la temperature selon T-3.08*0.05 et T-5.54*0.59 respectivement.Ces resultats, conjointement avec les resultats existants dans I'infrarouge montrent que r 2 est a toutes fins pratiques proportionnel a T-o.5 et que le rapport r 2 / r l vaut 0.91 a 296 K. Une mesure preliminaire concernant I'absorption induite dans H z est presentee. Les resultats pour les trois gaz ont ete compares aux resultats publies anterieurement dans la region des basses frequences.Can. J. Phys., 53, 1764Phys., 53, (1975 [Traduit par le journal]
The results of dielectric-constant measurements on a number of low-loss liquids in the microwave frequency region from 18 to 40 GHz are presented. Emphasis is placed on the value of the loss tangent. Liquids measured include carbon tetrachloride, carbon disulfide, cyclohexane, n-hexane, n-heptane, n-nonane, and n-decane. A wave guide method was used giving an accuracy for the loss tangent of ±0.3 × 10−4. Where possible, results have been fitted to a Debye expression. Comparisons have been made with available results of other workers.
The sideways displacement of an electromagnetic beam upon external reflection from a dielectric has been investigated. The experimental results, using 3 cm microwaves, are compared to those predicted by a theory based on a plane wave approach. The experiment has been completed for both perpendicular and parallel polarization as a function of total propagation distance at several angles of incidence around 45°.
Collision induced microwave absorption is reported in pure N2, N2–Ar, N2–CH4, mixtures, and in pure CH4 in the 35 and 70 GHz regions (1.1 and 2.3 cm−1) at a temperature of 22 °C. The measurements are accomplished using overmoded high Q cavities capable of pressurization of up to 5000 p.s.i.g. The apparatus and method are described. With the high sensitivity attained, the results in pure N2 from 30 → 250 amagat reveal terms in the square and cube of the density from which the relaxation times are calculated. The linear dependence on frequency of the collision induced absorption up to 2.3 cm−1 is established. Higher order dependence on the density is observed in the N2–Ar and N2–CH4 mixtures. Various estimates of the quadrupole moment of N2 are given, making use of earlier results in other frequency regions.
Collision-induced microwave absorption has been observed at 4.4 cm−1 for the inert gas mixtures Ne–Xe and Ar–Xe. The absorption coefficient has been measured at room temperature for a range of density products up to 15 000 amagat2 and for different density ratios. The intracollisional absorption coefficient has been determined at this low frequency for each mixture from the data at low densities. These results for the absorption coefficient along with existing infrared results have yielded an accurate value for the zeroth moment for each of the spectra and hence improved values for the induced dipole moment parameters for the exponential model. For the range parameter, ρ, we obtain values of 0.312 Å and 0.408 Å, respectively, for the Ne–Xe and Ar–Xe mixtures. The values for the dipole strength parameters, μσ, calculated using the Lennard-Jones (12-6) potential are 0.0293 and 0.0328 D, respectively. Evaluations of μσ have also been carried out using other potentials. In particular, for Ne–Xe a value of μσ = 0.0377 D is calculated using the more realistic Morse – Spine – van der Waals (MSV) potential. At higher densities the results reveal intercollisional interference effects which result in a reduction of the absorption. The amount of reduction depends on the ratios of the gases in the mixture. In the highest density range studied, there is observed a marked increase in the absorption which may be attributed to many-body collisions.
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