Atomic and molecular systems for radiation thermometry

TL;DR

This paper introduces atomic and molecular systems as new standards and sensors for radiation thermometry, demonstrating two experiments with promising accuracy and potential for primary temperature measurement.

Contribution

It presents a novel approach to radiation thermometry using atoms and molecules, including two experimental setups with detailed models and promising uncertainties.

Findings

Cold atom thermometer (CAT) achieves ~1% uncertainty in BBR spectrum near 130 GHz.

CoBRAS sensor measures blackbody spectrum near 24.5 THz with 0.13 K relative precision.

Both methods show clear paths toward primary temperature standards.

Abstract

Atoms and simple molecules are excellent candidates for new standards and sensors because they are both all identical and their properties are determined by the immutable laws of quantum physics. Here, we introduce the concept of building a standard and sensor of radiative temperature using atoms and molecules. Such standards are based on precise measurement of the rate at which blackbody radiation (BBR) either excites or stimulates emission for a given atomic transition. We summarize the recent results of two experiments while detailing the rate equation models required for their interpretation. The cold atom thermometer (CAT) uses a gas of laser cooled $^{85}$Rb Rydberg atoms to probe the BBR spectrum near 130~GHz. This primary, {\it i.e.}, not traceable to a measurement of like kind, temperature measurement currently has a total uncertainty of approximately 1~\%, with clear paths toward improvement. The compact blackbody radiation atomic sensor (CoBRAS) uses a vapour of $^{85}$Rb and monitors fluorescence from states that are either populated by BBR or populated by spontaneous emission to measure the blackbody spectrum near 24.5~THz. The CoBRAS has an excellent relative precision of $u(T)\approx 0.13$~K, with a clear path toward implementing a primary