The rotational spectrum, structure and dynamics of a benzene dimer

The low J (2 to 7) rotational spectrum of a symmetric-top benzene dimer has been obtained with a Balle/Flygare Fourier transform microwave spectrometer. Each transition is a symmetrical quartet with two J- and K-dependent tunneling splittings of 30 to 400 kHz. Rotational constants B̄, DJ, and DJK were determined to be 427.76(2) MHz, 7.2(3) kHz, and 0.869(5) MHz. The dimer is T-shaped with a benzene c.m. to c.m. distance of 4.96 Å.