Novel magnetic interactions in the open-shell NO–HF complex

The J′=3/2 (f)−J″=1/2 (f) rotational transition of the open-shell van der Waals complex NO–HF has been observed using a Fourier transform microwave spectrometer. The transition shows a rich hyperfine structure due to coupling of the NO electronic spin and orbital angular momenta with the N nucleus and also with both the H and F nuclei in a novel intermolecular magnetic hyperfine interaction. The N hyperfine coupling reveals the splitting of the Π state degeneracy into A′ and A″ states, with the A′ state lower in energy.