Knowledge Bank

The radio frequency and microwave spectrum of $K=0,J=0,1,2$ states of the hydrogen bonded complex HF:HC1 has been measured. The measured spectroscopic constants are \begin {eqnarray*}(B + C)/2 = 3422.461(5) MHz,\ D_{J} = 0.024(2) MHz,\ (eqQ){a} = - 52.291(10) MH{z},\ \mu a = 2.4095(5)D.\end {eqnarray*} The quadrupole data indicate that the HC1 unit has a vibrationally averaged $cosine2$ $\theta$ projection onto the principle inertial axis of $0.85(\cos (-1)cos2\theta =23\circ )$. $3.38$ {\AA} is the vibrationally averaged F-C1 distance. The structure and bonding of this hydrogen bonded complex will be discussed and the results will be compared with those of previously studied van der Waals’ molecules.