An analysis of the magnetic hyperfine interactions in the microwave spectrum of NO–HF: Evidence of electron transfer

One hundred and fifty-six magetic hyperfine transitions belonging to four rotational transitions of the NO–HF complex have been observed using a Fourier transform microwave spectrometer. The magnetic hyperfine structure shows interactions due to the nitrogen, hydrogen, and fluorine nuclei. Analysis of both the fine and hyperfine structure gives a bent geometry with an a axis–NO angle of about 44° and indicates a strong stabilization of the in plane NO π* orbital with respect to the out of plane orbital. The Fermi contact interactions at the H and F nuclei have the opposite sign and comparison with ab initio calculations suggests assigning the larger positive interaction to the F nucleus. The results reveal details of the distortions of the electronic structure of the partners in the complex caused by the hydrogen bond.