The experimental data was taken from
(1) R. D. Brown, P. D. Godfrey, and M. Rodler, 1986, J. Am. Chem. Soc. 108, 1296, from
(2) E. G. Robertson, P. D. Godfrey, and D. McNaughton, 2003, J. Mol. Spectrosc. 217, 123,
and from
(3) S. G. Kukolich, C. Tanjaroon, M. C. McCarthy, and P. Thaddeus, 2003, J. Chem. Phys. 119, 4353.
Predictions for transitions with higher quantum numbers or at higher frequencies, in particular much above 100 GHz, should be viewed with caution.
The dipole moment was taken from an ab initiocalculation by
(4) E. Craka and D. Cremer, 1993, Chem. Phys. Lett. 216, 333 .
The nuclear spin-weight ratio is 5 : 3 for ortho-c-C₆H₄ : para-c-C₆H₄. The ortho states are described by K_a + K_c even, the para states by K_a + K_c odd.