Optical determination of the Boltzmann constant

摘要

The Boltzmann constant k B is a fundamental physical constant in thermodynamics. The present CODATA recommended value of k B is 1.3806488(13) × 10-23J/K(relative uncertainty 0.91 ppm), which is mainly determined by acoustic methods. Doppler broadening thermometry(DBT) is an optical method which determines k B T by measuring the Doppler width of an atomic or molecular transition. The methodology and problems in DBT are reviewed, and DBT measurement using the sensitive cavity ring-down spectroscopy(CRDS) is proposed. Preliminary measurements indicate that CRDSbased DBT measurement can potentially reach an accuracy at the 1 ppm level.