Avoided crossings in the far-infrared laser magnetic resonance spectrum of HCO

Abstract Several transitions in the far-infrared spectrum of the HCO radical have been detected by the technique of laser magnetic resonance (LMR). The spectra have been assigned to both a - and b -dipole transitions and have been fitted together with previous microwave, millimeter-wave, and infrared measurements to determine a full set of parameters for HCO in its ground state. In particular, signals arising from the avoided crossing of the levels 8 08 and 7 16 in a magnetic field have been analyzed and used to determine values for the off-diagonal components of the spinrotation, proton dipolar hyperfine, and anisotropic g -tensors which are responsible for the mixing of the states. The reduced spin-rotation parameter ( ϵ ab + ϵ ba ) has been separated into its component parts by the imposition of the constraint ϵ ab ϵ ba = A B .