Quantitative atomic spectroscopy for primary thermometry

Abstract

Quantitative spectroscopy has been used to measure accurately the Doppler broadening of atomic transitions in 85Rb vapor. By using a conventional platinum resistance thermometer and the Doppler thermometry technique, we were able to determine kB with a relative uncertainty of 4.1 × 10-4 and with a deviation of 2.7 × 10−4 from the expected value. Our experiment, using an effusive vapor, departs significantly from other Doppler-broadened thermometry (DBT) techniques, which rely on weakly absorbing molecules in a diffusive regime. In these circumstances, very different systematic effects such as magnetic sensitivity and optical pumping are dominant. Using the model developed recently by Stace and Luiten, we estimate the perturbation due to optical pumping of the measured kB value was less than 4×10−6. The effects of optical pumping on atomic and molecular DBT experiments is mapped over a wide range of beam size and saturation intensity, indicating possible avenues for improvement. We also compare the line-broadening mechanisms, windows of operation and detection limits of some recent DBT experiments.