Incoherent broad-band cavity-enhanced absorption spectroscopy of the marine boundary layer species I-2, 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, I-2, IO and OIO, is reported. Absorption measurements of I-2 and OIO at lambda = 525-555 nm and IO at lambda = 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 similar to 26 pmol mol(-1) for I-2 (L = 81 cm, acquisition time 60 s), similar to 45 pmol mol(-1) for OIO (L = 42.5 cm, acquisition time 5 s) and similar to 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.