Interferometric Determination of Mean Polarizabilities and Second Density Virial Coefficients of Methane Between 128 K and 890 K

Abstract

Mean dynamic dipole polarizabilities α0(λ, T) and second thermodynamic virial coefficients B(T) of meth‐ane have been determined for the first time in the extended temperature range 128 K ≦ T ≦ 890 K by means of only one apparatus using interferometric low‐pressure measurements (p ≦ 03 MPa) of the refractive index n(λ, T, p) in the visible wavelength range (λ = vacuum wavelength). α0(λ, T) is in good accordance with previously measured values, but an obvious small minimum at the critical temperature Tc seems to occur. The B(T)‐data determined in the low‐temperature range ΔT1 (128 K ≦ T ≦ 298 K) are in fair agreement with other published data. The high‐temperature B(T)‐values of the range ΔTII (760 K ≦ T ≦ 890 K) have been measured for the first time. They are in good accordance with extrapolated low‐temperature virial coefficients. The mean standard deviation | ΔB | ≈ 8 cm3 mol−1 of the measured B(T)‐values may be further reduced by means of more precise measurements of pressure p.

Infrared absorption by collisional CH4+X pairs, with X=He, H2, or N2

“…Temperature variations of the polarizability of CH 4 have been reported [30][31][32] which are also related to rotovibrationinduced frame distortions. A strong dependence of the rotation-induced corrections on the rotational state is again noted.…”

Subcritical and supercritical thermodynamic properties of compressed Xe and Cl2 fluids

“…Recently Hohm and Trümper have determined B 2 (T) values of chlorine and xenon gases by interferometric refractive index measurements (at λ = 632.9 nm) [7][8][9][10][11], over the wide temperature range 290-1100 K [7]. In this method, the gas is interacted by a laser beam and a coupled Michelson interferometer is used to determine the refractive index.…”