A novel mid-infrared hollow waveguide gas sensor for measuring water vapor isotope ratios in the atmosphere

摘要

A novel mid-infrared hollow waveguide gas sensor was developed to target H218O, H216O, H217O, and HDO ab-sorption lines at 3662.9196, 3663.04522, 3663.32128, and 3663.84202 cm-1, respectively, based on wavelength modulation spectroscopy using a 2.73 mu m distributed feedback diode laser. A hollow waveguide fiber with a 5-m length and 1-mm inner diameter was used for gas absorption. A dew point generator with liquid water with known water-isotope ratios was used to calibrate the sensor. Detection limits of 35.18 ppbv, 4.69 ppmv, 60.53 ppbv, and 3.88 ppbv were obtained for H218O, H216O, H217O, and HDO, respectively, in a 96-s integration time, which resulted in isotopic ratio measurement precision of 0.85%0, 0.57%0, and 10.48%0 for 818O, 817O, and 8D, respectively. Field measurements of H218O, H216O, and H217O concentration were conducted on the Nanchang Hangkong University campus to evaluate sensor performance.

关键词