A transportable spectrometer for in situ and local measurements of iodine monoxide at mixina ratios in the 10~(-14) ranae

摘要

We present a robust, compact, and transportable instrument that measures the iodine monoxide atmospheric radical at extremely low concentration, down to 40ppqv (parts per quadrillion by volume, 1:10~(15)). As nitrogen dioxide is strongly absorbed in the same spectral region it could be simultaneously measured down to 4pptv (parts per trillion by volume, 1:10~(12)). 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.