Knowledge Bank

Rotational spectra for the two-structural isomers of the $N2O$-HF and $N2O$-DF complexes were measured using a pulse-beam, Fourier transform microwave spectrometer. Rotational transitions were measured to an accuracy of 10 kHz for ONN-HF and ONN-DF. These data were fit to obtain values for B and $DJ$. These data are consistent with linear or nearly linear structures with the H of HF bonded to the terminal N of $N2O$. A pseudo-diatomic analysis was used to obtain values for the force constant $ks$ and the stretching frequency $\nu 5$ of the weak bond. Thirteen new transitions were measured to an accuracy of 60 kHz for the bent structural isomers, NNO-HF and NNO-DF. These data, combined with previous microwave data were fit to obtain values for $(A+\Delta k),B$, and C, and four quartic distortion parameters, $\Delta J,\Delta Jk,\delta k$ and $\delta k$. The centrifugal distortion constants were used in an analysis of the stretching and bending force field parameters $fRR$ and $f99$. The bending force constant $fee$ is very small, indicating a large amplitude in-plane bending vibration due to the zero-point energy. The contribution of the H(D) atom to centrifugal distortion parameters is shown to be very small, and this results in a considerable simplification of the analysis.