Non-uniform Line-of-Sight Measurements of Nitric Oxide Mid-infrared Faraday Rotation Spectroscopy

Traditional absorption spectroscopy relies on detecting intensity variations along the line-of-sight to gauge average concentration and temperature. While methods like profile fitting and temperature binning offer insights into the non-uniformity of the path, they fall short of accurately capturing the precise spatial distribution with a single line-of-sight measurement. We propose a novel measurement scheme for non-uniformly distributed concentration of nitric oxide along the line-of-sight utilizing a single laser and path, by incorporating Faraday rotation spectroscopy with magnetic fields changing over time and space. We validate the proposed scheme by measuring a path of two regions in series with different NO concentrations and comparing the measurement results with direct absorption spectroscopy of each respective region. The average relative uncertainty in the concentration measurement for each region is estimated to be within 1.5%.