Infrared Spectrum of the Matrix‐Isolated OH Radical

Infrared absorption in the region of 3450 cm−1 has been observed in water–rare‐gas matrices subjected to vacuum‐ultraviolet photolysis at 20.4° and 4.2°K. The splittings and isotope frequency ratios obtained from H216O–D216O, H216O–H218O, and D216O–D218O mixtures lead to the assignment of these spectra to trapped OH radicals. No evidence for rotational motion of OH is found in these experiments.