A transportable spectrometer for in situ and local measurements of iodine monoxide at mixing ratios in the 10-14 range
Résumé
We present a robust, compact, and transportable instrument that measures the iodine monoxide atmospheric radical at extremely low concentration, down to 40 ppqv (parts per quadrillion by volume, 1:1015). As nitrogen dioxide is strongly absorbed in the same spectral region it could be simultaneously measured down to 4 pptv (parts per trillion by volume, 1:1012). Relying on ''mode locked cavity-enhanced absorption spectroscopy,'' the instrument makes use of a free-running commercial femtosecond Titane Saphir laser. We demonstrate that this multiplex detection scheme provides shot noise limited spectra for acquisition times as long as 5 min. Moreover, this instrument is very versatile as it can be potentially tuned from the infrared to the ultraviolet (1080-340 nm) to reach various molecular absorptions. It has been recently deployed at the Station Biologique de Roscoff on the North West Atlantic coast of France.
Mots clés
chemical variables measurement
gas sensors
infrared spectra
measurement by laser beam
shot noise
ultraviolet spectra
ultraviolet spectrometers
Sensors
remote sensing
Lasers
Metrological applications
optical frequency synthesizers for precision spectroscopy
Chemical analysis and related physical methods of analysis