First observation of the OIO molecule by time-resolved flash photolysis absorption spectroscopy

In the time-resolved flash photolysis of I2 in O3, in addition to the IO electronic bands between 21500 and 26000 cm−1, a new absorption spectrum has been observed between 15000 and 21500 cm−1, which is attributed to the Ã-X̃ electronic bands of the OIO radical. A number of spectroscopic constants of the à state of OIO were determined by linear least-squares fitting the observed spectrum: ν1 (symmetric IO stretch) ω1 = 631 cm−1, ν1 anharmonicity constant ω1χ1 = 2.6 cm−1, ν2 (OIO angle bend) ω2 = 177 cm−1, electronic energy with respect to the ground state Te = 14553 cm−1. These values are in good agreement with those expected from measurements of the same electronic bands in OClO and OBrO.