Dielectric-Constant Gas Thermometry and the Relation to the Virial Coefficients

Theoretical determination of polarizability and magnetic susceptibility of neon

“…(2) 0 (X)] or finite-difference approach [for α (2) n (X), n ≥ 2]. In the case of static polarizability, the expectation values of the operators from Eqs.…”

“…The connection between the microscopic quantities, α and χ, and the macroscopic ones, ǫ r and µ r , becomes particularly important if one notices that the latter two are directly accessible by experimental techniques. The relative electric permittivity can be determined from capacitance measurements [2][3][4][5][6] with accuracy reaching one part per million. In fact, such measurements (dielectricconstant gas thermometry) are the source of currently most accurate experimental values of atomic polarizabilities [7].…”

“…The refractive index can be measured by several microwave [8] and optical methods [9,10]. * e-mail: lesiuk@tiger.chem.uw.edu.pl Development of new experimental techniques [2][3][4][5][6][7][8][9][10] has been critical for the progress in modern thermal metrology. For example, it has been proposed to establish a new pressure standard based on the measurements of ǫ r , or on laser refractometry measurements of the refractive index [10].…”

“…Since the value of the Boltzmann constant k is now fixed according to the new SI definition of the unit of temperature T [11,12], the knowledge of α and χ is required to obtain p directly from n, via Eq. (2). A significant portion of the experimental effort in this field targets noble gases due to numerous favorable properties such as being chemically inert and stable, etc.…”

“…Since χ is about five orders of magnitude smaller than α, it does not have to be known with very high accuracy when used in Eq. (2). Therefore, we determine χ using the nonrelativistic theory.…”