title: Long-path monitoring of NO2 with a 635 nm diode laser using frequency-modulation spectroscopy.
abstract: In situ monitoring of traffic-generated nitrogen dioxide (NO2) emissions using long-path absorption spectroscopy is reported. High-sensitivity detection of NO2 is achieved by employing two-tone frequency-modulation spectroscopy at a visible absorption band using a tunable high-power diode laser operated around 635 nm. A real-time absorption spectrometer is accomplished by repetitively applying a rectangular current pulse to the diode-laser operating current, allowing detection of isolated NO2 absorption lines. A detection limit of 10 microg/m3 for NO2 at atmospheric pressure using a 160 m absorption path is demonstrated. Continuous monitoring of NO2 over a road intersection at peak traffic is performed.
authors.affiliation: Department of Physics, Lund Institute of Technology, P.O. Box 118, S-22100 Lund, Sweden.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Somesfalean
authors.forename: Janis
authors.initials: J
authors.lastname: Alnis
authors.forename: Ulf
authors.initials: U
authors.lastname: Gustafsson
authors.forename: Hans
authors.initials: H
authors.lastname: Edner
authors.forename: Sune
authors.initials: S
authors.lastname: Svanberg