Our understanding of the electronic structure of molecules often comes from spectroscopic
investigations in which electromagnetic radiation is applied to a molecule and the scattering …

We review the principles, techniques and results from primary acoustic gas thermometry
(AGT). Since the establishment of ITS-90, the International Temperature Scale of 1990 …

The adiabatic, relativistic, and quantum electrodynamics (QED) contributions to the pair
potential of helium were computed, fitted separately, and applied, together with the …

Since the beginning of measurement of pressure in the 17th century, the unit of pressure has
been defined by the relationship of force per unit area. The present state of optical …

Recent advances regarding the interplay between ab initio calculations and metrology are
reviewed, with particular emphasis on gas-based techniques used for temperature and …

A recent argon–argon interatomic potential energy curve determined from quantum-
mechanical ab initio calculations and described with an analytical representation [B. Jäger …

Using a quasispherical, microwave cavity resonator, we measured the refractive index of
helium to deduce its molar polarizability A ε in the limit of zero density. We obtained (A ε …

The refractive index n of gaseous helium can be measured by optical interferometry so
accurately that it can be used to establish a pressure standard which is expected to be …

The redefinition of the kelvin has increased focus on thermometry techniques that use the
newly fixed value of the Boltzmann constant to realize thermodynamic temperature. One …

The principles and techniques of primary refractive-index gas thermometry (RIGT) are
reviewed. Absolute primary RIGT using microwave measurements of helium-filled quasi …