Knowledge Bank

Rotational transitions of the dimers $HCOOH\cdot \cdot CF3COOH$ and $CH3COOH\cdot \cdot CF3COOH$ have been observed in a pulsed molecular beam with a Fabry-Perot cavity spectrometer. The monomer units are connected with two hydrogen bonds forming a planar eight-membered ring. Transitions with J between 6 and 15 have been assigned over 8 - 12 GHz. The K structure of the nearly prolate symmetric rotors was completely resolved. No splittings were found for hydrogen tunneling between the equivalent positions in the two hydrogen bonds. The internal rotation splittings of the CF3 groups were too small to be observed. Only the internal rotation of the CH3 group led to splittings of the order of 1-40 MHz.