Sensitive and selective detection of O H radicals using Faraday rotation spectroscopy at 2.8 μm
Résumé
We report on the development of a Faraday rotation spectroscopy (FRS) instrument using a DFB diode laser operating at 2.8 μm for the hydroxyl (OH) free radical detection. The highest absorption line intensity and the largest gJ value make the Q (1.5) double lines of the 2∏3/2 state (ν = 1 ← 0) at 2.8 μm clearly the best choice for sensitive detection in the infrared region by FRS. The prototype instrument shows shot-noise dominated performance and, with an active optical pathlength of only 25 cm and a lock-in time constant 1E8 OH radicals/cm3