Atomic and Molecular Systems Enable 130GHz Radiation Thermometry with Primary, Non-traceable Measurements

The quest for more accurate and reliable temperature standards drives innovation in physics and metrology, and recent work by Stephen P. Eckel, Eric B. Norrgard, and Christopher L. Holloway, along with colleagues at the National Institute of Standards and Technology, presents a significant advance in radiation thermometry. These researchers explore the potential of utilising atoms and molecules as the basis for new temperature standards, leveraging their inherent uniformity and the predictable laws governing their behaviour. They demonstrate two experimental approaches, the cold atom thermometer and the compact blackbody radiation atomic system, which both measure blackbody radiation to determine temperature with unprecedented precision. This work establishes a pathway toward primary temperature measurements, independent of existing standards, and promises improvements in fields ranging from industrial process control to fundamental physics research. 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 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 Rb Rydberg atoms to probe the BBR spectrum near 130GHz. This primary, i. e., not traceable to a measurement of like kind, temperature.

Atomic Transitions Measure Blackbody Radiation Temperature This research explores the potential of using atoms and molecules as the basis for a new generation of radiation thermometers, aiming for increased accuracy and stability, potentially achieving a primary standard independent of traditional calibration. The core idea centres around the interaction of blackbody radiation, the most fundamental source of electromagnetic radiation, with atoms and molecules. Blackbody radiation induces transitions between energy levels within atoms and molecules, and by precisely measuring these transitions, one can determine the temperature of the source. The research demonstrates the feasibility of using Rydberg atoms in cold atom setups to measure the temperature of millimetre-wave blackbody radiation with high precision. Scientists also explore using optically excited atoms within vapour cells as a more compact and practical platform for blackbody thermometry, aiming for sensors that are smaller, more robust, and easier to deploy. The research extends to investigate the use of polyatomic molecules and luminescence-based techniques for thermometry, including exploring fluorescence intensity ratio thermometers based on rare-earth and transition metal ions doped inorganic luminescent materials. Future research will focus on improving the accuracy of atomic property calculations, exploring new materials for sensor development, and creating sensors for a wider range of temperatures and wavelengths. In essence, the paper presents a compelling case for a paradigm shift in radiation thermometry, moving towards sensors based on fundamental atomic and molecular properties rather than relying on traditional calibration standards, with potential applications in metrology and remote sensing.

Atomic Radiative Thermometry Achieves High Precision Scientists are developing new standards for measuring temperature using atoms and molecules, leveraging their inherent consistency and properties dictated by fundamental physics. This work introduces a method for building a radiative temperature standard based on precise measurements of how blackbody radiation excites or stimulates emission from specific atomic transitions. Recent experiments utilizing both cold rubidium atoms and rubidium vapour demonstrate the feasibility of this approach, paving the way for primary temperature standards not reliant on calibration against other thermometers. The cold atom thermometer (CAT) employs laser-cooled rubidium atoms to probe the blackbody radiation spectrum near 130GHz, currently achieving a total uncertainty of approximately one percent, with ongoing research focused on further improvements to its precision. Simultaneously, the compact blackbody radiation atomic sensor (CoBRAS) utilizes rubidium vapour to monitor fluorescence resulting from blackbody radiation or spontaneous emission, enabling measurements of the blackbody spectrum near 24. 5THz and recording temperature variations with a resolution of approximately 0. 13 K. These experiments demonstrate that the rate of atomic transitions is directly linked to temperature through fundamental constants and atomic properties. By carefully measuring these transition rates, scientists can determine temperature with high accuracy and establish a primary standard, independent of external calibration. Calculations reveal that the precision of this atomic thermometer scales with the number of atoms probed, suggesting that measuring approximately 10 10 atoms could achieve a relative uncertainty of 10 -5 .

This research highlights the potential for atoms and molecules to serve as highly accurate and reliable temperature standards across a broad range of frequencies and temperatures. Atomic Thermometry via Blackbody Radiation Measurement Recent research has demonstrated the feasibility of establishing new temperature standards based on the precise measurement of blackbody radiation using atoms and molecules.

Scientists have developed two distinct experimental approaches, the cold atom thermometer (CAT) and the compact blackbody radiation atomic sensor (CoBRAS), to probe the blackbody spectrum at different frequencies. The CAT utilizes laser-cooled rubidium Rydberg atoms to measure radiation near 130GHz, achieving a total uncertainty of approximately one percent with potential for further refinement. Complementing this, the CoBRAS instrument employs rubidium vapour to monitor fluorescence at 24. 5THz, exhibiting excellent relative precision at the level of kelvins. These advancements represent a significant step towards primary temperature measurements, independent of traditional standards. Researchers acknowledge that current limitations stem from systematic uncertainties within the experiments, particularly in determining initial state populations and accounting for complex atomic interactions. However, they suggest that improvements in optical pumping techniques and selective field ionization could reduce uncertainties to below 0. 1%, approaching the accuracy of established microwave blackbody sources and radiometers. 👉 More information 🗞 Atomic and molecular systems for radiation thermometry 🧠 ArXiv: https://arxiv.org/abs/2512.08668 Tags: