The Electric And Magnetic Susceptibilities Of Gaseos Oxygen: Comparisons Of New Measurements and Modern Theory

Published

September 25, 2008

Author(s)

Michael R. Moldover, E May, James W. Schmidt

Abstract

We used a cross capacitor to measure the relative dielectric permittivity ε_r of O₂ at 273 K, 293 K, and 323 K and at pressures up to 6.5 MPa. Simultaneously we measured oxygen's complex refractive index n using a quasi-spherical cavity resonator at frequencies between 2.4 GHz and 7.3 GHz. The combined results from these measurements determine oxygen's frequency-dependent, relative magnetic permeability, υ_r(f, p, T), with an uncertainty of less than 1 % of (υ_r – 1) at pressures above 2 MPa. Regression of these data to a model for oxygen's impact-broadened microwave spectrum allowed us to determine two quantities that are, in principle, amenable to calculation: the molar magnetic susceptibility in the limits of zero-pressure and zero-frequency: χ_meas,M000=χ_M(0,0,293.15 K), and the second magnetic virial coefficient, b_υ. With oxygen's electronic g-factor constrained to 2.0039 {plus or minus} 0.0003 (the value known from laser magnetic resonance, EPR and molecular beam experiments), we obtained χ_meas,M000 = (42.92 {plus or minus} 0.06)×10^–9 m³ mol^–1 and b_υ=(–1.8 {plus or minus} 0.5) cm³ mol^–1. The result for χ_meas,M000 is consistent with a recent ab initio calculation: χ_meas,M000/χ_calc,M000 = 0.9998 {plus or minus} 0.0014. Our measurements of oxygen's magnetic susceptibility are the first made relative to the susceptibility of helium calculated ab initio. All previous measurements were made relative to the diamagnetic susceptibility of water. These previous measurements, published in 1943 or earlier, span the wider range 0.975 {less than or equal to} χ_meas,M000/χ_calc,M000 {less than or equal to} 1.019. Our measurements of ε_r determine the static molecular dielectric polarizability of oxygen: (1.7456 {plus or minus} 0.0003)×10^–40 C² m² mol^–1, which deviates by +0.7 % and –0.1 % from two recent ab initio calculations.

Citation

Physical Review A (Atomic, Molecular and Optical Physics)

Volume

78

Issue

9/25/2008

Pub Type

Journals

Keywords

electric susceptibility, dielectric constant, magnetic permeability, magnetic susceptibility, relative magnetic permeability, oxygen, paramagnetism, refractive index

Citation

Moldover, M. , May, E. and Schmidt, J. (2008), The Electric And Magnetic Susceptibilities Of Gaseos Oxygen: Comparisons Of New Measurements and Modern Theory, Physical Review A (Atomic, Molecular and Optical Physics) (Accessed December 4, 2024)