Long-path monitoring of NO2 with a 635 nm diode laser using frequency-modulation spectroscopy.
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.
Somesfalean
Gabriel
G
Department of Physics, Lund Institute of Technology, P.O. Box 118, S-22100 Lund, Sweden.
Alnis
Janis
J
Gustafsson
Ulf
U
Edner
Hans
H
Svanberg
Sune
S