The observed lines are from
(1) A. J. Alexander, H. W. Kroto, M. Maier, and D. R. M. Walton, 1978, J. Mol. Spectrosc. 70, 84.
The purely K-dependent parameters (A and D_K), needed to obtain reasonable intensities, were taken from CH₃CCH;
(2) H. S. P. Müller, P. Pracna, and V.-M. Hornemann, 2002, J. Mol. Spectrosc., 216, in press.
The dipole moment is an estimate from
(3) M. Bester, K. M. T. Yamada, G. Winnewisser, W. Joentgen, H.-J. Altenbach, and E. Vogel, 1984, Astron. Astrophys. 137, L20.
Predictions above 100 GHz should be viewed with caution. At low temperatures, it may be necessary to discern between A-CH₃C₆H and E-CH₃C₆H. The A states are described by K = 3n, the E states by K = 3n ± 1. The nuclear spin-weight ratio is 2 : 1 for A-CH₃C₆H with K > 0 and all other states, respectively. The J_K = 1₁ state is the lowest E state. It is 5.3342 cm^–1 above ground.