Knowledge Bank

The structure of the hydrogen bonded complex formed between $NH3$ and HF has been determined by molecular beam electric resonance spectroscopy. The complex exhibits a rotational spectrum that is characteristic of a symmetric top, implying an effectively linear hydrogen bond. The rotational, centrifugal distortion, and nuclear quadrupole coupling constants have been precisely determined with values as follows: [B = 7366.11(2)\ MHz, D_{J} = 28.3(20)\ KHz, (eQq)_{a} = -3.283(70)\ MHz.] The electric dipole moment of the complex has also been determined, $\mu =4.448(1)$ D, from measurements of the Stark effect. Assuming that the structure of ammonia is unchanged upon complex formation the N-F distance (2.660{\AA}) is found to be much shorter than has been predicted by recent \emph{ab initio} calculations.