The rotational spectra of six isotopomers of the linear and bent isomers of HF-N 2 O have been collected in the 7-18 GHz region with a Fourier transform microwave spectrometer. The nuclear hyperfine structure in the spectra produced by HF spin-spin coupling interaction and nuclear quadrupole coupling interactions due to the D nucleus of DF and the 14 N nuclei of N 2 O have been resolved and analyzed. In the linear isomer, H in HF is bonded to the terminal N in N 2 O. The NF bond lengths are 2.9808(2)
A A for the HF-containing isotopomers and 2.9732(2)
A A for the DF-containing isotopomers. The zero point angles are 23.1°for HF and 31-34°for N 2 O. The hyperfine constants suggest that the HF bond is lengthened by 0.0105 A A upon complexation and that the electric field gradients of the two nitrogen nuclei in N 2 O are perturbed differently in the complex. In the bent isomer, the hydrogen bond is formed between HF and O in N 2 O. The intermolecular distances are 3.4942(2)
A A for the HF-containing isotopomers and 3.4436(2)
A A for the DF-containing isotopomers, with HF and N 2 O forming angles of 34°and 46°, respectively, with the intermolecular axis. The nuclear quadrupole coupling constants of the two nitrogen nuclei do not indicate electric field gradient perturbation in this isomer.