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Updated: Jun 4, 2026

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Sensitive and selective detection of OH radicals using Faraday rotation spectroscopy at 2.8 µm
Weixiong Zhao1, Gerard Wysocki, Weidong Chen
1Laboratoire de Physicochimie de l’Atmosphère, Université du Littoral Côte d’Opale, 189A Av Maurice Schumann, 59140 Dunkerque, France.
Abstract:
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 2Π3/2 state (υ = 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 of 100 ms, achieves a 1σ detection limit of 8.2 × 10(8) OH radicals/cm3.
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