Quantitative atomic spectroscopy for primary thermometry

TL;DR

This paper demonstrates a precise method for primary thermometry using Doppler-broadening in atomic spectroscopy of rubidium vapor, achieving high accuracy and analyzing systematic effects like optical pumping.

Contribution

It introduces a novel Doppler thermometry technique with atomic vapor, providing a new approach to primary thermometry with detailed analysis of systematic effects.

Findings

Achieved a relative uncertainty of 4.1×10^{-4} in determining Boltzmann's constant.

Estimated optical pumping perturbation on measured k_B was less than 4×10^{-6}.

Compared line-broadening mechanisms and detection limits across recent DBT experiments.

Abstract

Quantitative spectroscopy has been used to measure accurately the Doppler-broadening of atomic transitions in $^{85}$Rb vapor. By using a conventional platinum resistance thermometer and the Doppler thermometry technique, we were able to determine $k_B$ with a relative uncertainty of $4.1\times 10^{-4}$, and with a deviation of $2.7\times 10^{-4}$ from the expected value. Our experiment, using an effusive vapour, 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 $k_B$ value was less than $4\times 10^{-6}$. 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.