Incoherent broad-band cavity-enhanced absorption spectroscopy of the marine boundary layer species I₂, IO and OIO

The novel combination of incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS) and a discharge-flow tube for the study of three key atmospheric trace species, I₂, IO and OIO, is reported. Absorption measurements of I₂ and OIO at λ = 525-555 nm and IO at λ = 420-460 nm were made using a compact cavity-enhanced spectrometer employing a 150 W short-arc Xenon lamp. The use of a flow system allowed the monitoring of the chemically short-lived radical species IO and OIO to be conducted over timescales of several seconds. We report detection limits of ∼26 pmol mol^-1 for I₂ (L = 81 cm, acquisition time 60 s), ∼45 pmol mol^-1 for OIO (L = 42.5 cm, acquisition time 5 s) and ∼210 pmol mol^-1 for IO (L = 70 cm, acquisition time 60 s), demonstrating the usefulness of this approach for monitoring these important species in both laboratory studies and field campaigns.