FTIR spectroscopic observation of gaseous HOI

Abstract Medium resolved infrared spectra (Δν = 1 cm −1 ) have been recorded in the wave-number range 4000-600 cm −1 of the products formed in the 254 nm photolysis of I 2 H 2 O 2 , CH 3 IH 2 O 2 and CH 2 I 2 H 2 O 2 gas mixtures at a total pressure of 1013 mbar of N 2 at 298 ± 2 K in a 1080 l glass reaction chamber. In all of the reaction systems studied absorption features were observed with band centers at approximately 3620 and 1070 cm −1 which have been assigned to the ν 1 OH stretching and ν 2 bending modes of gaseous hypoiodous acid (HOI), respectively. This represents the first report of the gaseous IR spectrum of HOI. The investigations provide the first conclusive evidence that the reaction of OH with I 2 leads to the formation of HOI. The lifetime of HOI in the chamber was only 1–2 min and was too short to allow any studies on the chemistry of HOI with the applied experimental technique.