FAR-INFRARED SPECTRUM OF HO2

We have measured the frequencies of 17 transitions in the far-infrared spectrum of the hydroperoxyl radical, HO2, from 2.5 to 5.9 THz, encompassing rotational levels up to N = 19 and K--1 = 5. These measured transition frequencies are combined with previously measured microwave and millimeter-wave transition frequencies in a complete reanalysis of the HO2 Hamiltonian for the ground vibrational state, including spin-rotation and nuclear hyperfine interactions. A revised set of molecular constants is presented. These include centrifugal distortion effects through octic dependence on the rotational angular momentum and the off-diagonal tenser component of the spin-spin dipolar interaction between the proton and the unpaired electron spin. (C) 1995 Academic Press, Inc.