The σ‐Hole Interaction Between Sulfur Hexafluoride and Ammonia Characterised by Broadband Rotational Spectroscopy

A weakly‐bound complex of SF 6 and NH 3 is generated within an expanding gas jet and characterised by broadband rotational spectroscopy. The spectra of isotopologues 32 SF 6 ⋅⋅⋅ 14 NH 3 , 32 SF 6 ⋅⋅⋅ 14 ND 3 , 32 SF 6 ⋅⋅⋅ 15 NH 3 and 34 SF 6 ⋅⋅⋅ 15 NH 3 are observed and assigned to determine the spectroscopic parameters. These parameters are consistent with the complex having a C 3 v symmetric rotor geometry, in which the nitrogen atom of NH 3 coordinates to SF 6 such that the C 3 v axis of the NH 3 sub‐unit is aligned with a local C 3 axis on the SF 6 sub‐unit. The geometry of the complex is rationalized in terms of a σ‐hole interaction. The observed spectra and ab initio calculations also reveal evidence of internal dynamics involving internal rotation of one monomer sub‐unit with respect to the other about the symmetry axis of the complex.