Doppler Broadening Thermometry by means of dual-laser absorption spectrometry at 1.39 μm

We report on the recent advances towards the development of low-uncertainty Doppler broadening thermometry, based upon precision molecular spectroscopy in the near-infrared region, for the aims of the spectroscopic determination of the Boltzmann constant. In the 3rd-generation experiment, our goal is to further reduce the global uncertainty as compared to previous determinations [1, 2], thus approaching the target accuracy of one part in 106.