Far infrared laser magnetic resonance detection of CHD (X̃ 3A

Far infrared laser magnetic resonance (FIR‐LMR) spectra of the CHD radical in its X3A‘ electronic ground state were observed and assigned. The radicals were generated in the reaction of Na atoms with CHDBr2. LMR spectra were observed using seven laser lines at wavelengths around 100 to 200 μm. The spectra were assigned to six different rotational transitions and the molecular parameters of CHD were determined by a least squares fit. A number of additional transitions, observed using a laser line at λ=184.3 μm but not yet assigned in detail, were attributed to a coupling between the accidentally almost degenerate NKaKc=505 and 413 rotational levels induced by the eab term in the spin–rotation Hamiltonian and by the off‐diagonal components of the hyperfine coupling tensor.