Abstract

The HOCO radical is crucially important in combustion chemistry as the intermediate in the reaction between hydroxyl radicals and carbon monoxide. Studies of the temperature dependence of the rate constant for this reaction implied the existence of the radical intermediate¹ but only very recently was HOCO detected in the gas phase^2,3. Both the infrared spectrum³, which is due to the perturbed C=O stretching fundamental (v₂), and the observed rotational spectrum² consist only of a-dipole transitions. Such transitions obey the selection rule ΔK_a = 0 in this near prolate top rotor and as such contain no direct information on the spacings between energy levels of different K_a. The high precision of the millimeter wave data allowed an approximate value for the A rotational constant to be derived² however the accuracy with which it is known is much less than for B and C. Nonetheless, when combined with data for DOCO, it was possible to unequivocally attribute the spectra as due to the trans- geometrical isomer of the radical².

© 1993 Optical Society of America