Primary gas thermometry by means of laser-absorption spectroscopy: Determination of the Boltzmann constant

TL;DR

This paper presents a novel laser absorption spectrometry method for primary gas thermometry that accurately measures the Boltzmann constant by analyzing Doppler broadening in CO₂ gas over a wide temperature range.

Contribution

It introduces a new optical implementation for gas thermometry using laser absorption spectroscopy to determine the Boltzmann constant with high precision.

Findings

Achieved a relative accuracy of ~1.6×10⁻⁴ in Boltzmann constant measurement.

Demonstrated the method's effectiveness across temperatures from water triple point to gallium melting point.

Provided a new approach for fundamental constant determination using spectroscopic techniques.

Abstract

We report on a new optical implementation of primary gas thermometry based on laser absorption spectrometry in the near infrared. The method consists in retrieving the Doppler broadening from highly accurate observations of the line shape of the R(12) $\nu_{1} + 2 \nu_{2}^{\phantom{1}0} + \nu_{3}$ transition in CO$_{2}$ gas at thermodynamic equilibrium. Doppler width measurements as a function of gas temperature, ranging between the triple point of water and the gallium melting point, allowed for a spectroscopic determination of the Boltzmann constant with a relative accuracy of $\sim1.6\times10^{-4}$.