Knowledge Bank

The rotational spectrum of the weakly bound dimer of carbonyl sulfide (OCS) and fluoroform (HCF$3$) has been assigned using Fourier-transform microwave spectroscopy. The rotational constants for the normal isotopomer are $A=4745.7157(25)$ MHz, $B=813.9222(27)$ MHz, and $C=790.9238(27)$ MHz, and dipole moment components are $\mu a=0.828(4)$ D and $\mu b=0.858(7)$ D. The experimental rotational constants are found to be in very good agreement with ab initio optimizations at the MP2/6-311++G(2d,2p) level of calculation. This $Cs$ symmetry structure has the OCS and HCF$3$ aligned such that there is a C--H...O and C--F...C interaction, with an approximate C...C intermolecular distance of 3.60 \AA.