NIST’s Daniel Herman will implement the new research results at the Optica Imaging and Applied Optics Congress, which will take place from July 11th to 15th, 2022. Herman’s presentation is planned for July 11th, 2022, at 11:45 am. PDT.
To analyze isotopologues in atmospheric water vapor, researchers now depend on connections of point sensors. Although these networks are growing in size, careful calibration is required to maintain precision over time and between sites.
Identifying water vapor in an open-air path may remove the need for quantification and make large-scale evaporation above reservoirs or across complete watersheds simpler to acquire.
To identify different water vapor isotopologues in the air, a mid-infrared spectrometer with a high spectral resolution, good precision, and quick measurement rates is required. Herman and colleagues achieved this by developing a new open-path mid-infrared dual-comb spectrometer (DCS) that utilizes near-infrared femtosecond laser pulses and specially built waveguides to generate broadband mid-infrared pulses in a small form.
The scientists put the new instrument to the test by taking measurements over a 760-meter path at Colorado’s Platteville Atmospheric Observatory. They discovered that the instrument is able to function in the field for weeks without human intervention. This permitted them to collect data for several months in a wide range of weather and temperature conditions.
The DCS measurements are well correlated with those obtained using a point sensor network, indicating the potential for open-path DCS in characterizing atmospheric water vapor.
Herman adds, “To expand isotopologue measurement networks, we are working to improve the accuracy of our technique by analyzing systematics in the detection setup. The sensitivity of the technique can be improved by using higher power combs to enable longer paths. Also, balanced detection technology will be implemented in the future to decrease technical noise.”