Detection of Nitric Oxide with Faraday Rotation Spectroscopy at 5.33 μm

We report the development of a static magnetic field Faraday rotation spectrometer for NO detection. A 5.33 μm continuous-wave quantum cascade laser was used as the probing laser. Line absorption at 1875.81 cm^-1 (^2\Pi_3/2Q(3/2), v=1\leftarrow0) was chosen for the detection. By using a Chernin type multipass cell, a detection precision of 1.15 ppbv (1\sigma, 1s) was achieved with an absorption pathlength of 108 m. This value was reduced to 0.43 ppbv by increasing the data-acquisition time to 15 s.