The experimental data were taken from
(1) N. Heineking, H. Dreizler, R. Schwarz, 1986, Z. Naturforsch. A 41, 1210;
from
(2) F. Mata, M. J. Quintana, and G. O. Sørensen, 1977, J. Mol. Struct. 42, 1;
from
(3) G. O. Sørensen, L. Mahler, N. Rastrup-Adersen, 1974, J. Mol. Struct. 20, 119;
from
(4) A. Maris, L. B. Favero, R. Danieli, P. G. Favero, and W. Caminati, 2000, J. Chem. Phys. 113, 8567;
from
(5) G. Wlodarczak, L. Martinache, J. Demaison, B. P. van Eijck, 1988, J. Mol. Spectrosc. 127, 200;
from
(6) E. Ye, R. P. A. Bettens, F. C. De Lucia, D. T. Petkie, and S. Albert, 2005, J. Mol. Spectrosc. 232, 61.
Similar to (4) and (5), Watson's S-reduction was used. The parameter set is equivalent to the one in (6). ¹⁴N hyperfine structure was deemed to be irrelevant for astronomical observations and were omitted. Few lines from (6), already weighted out there, were omitted from the fit.
The predictions are deemed to be sufficient for all needs of astronomers. Predictions with uncertainties larger than 0.5 MHz should be viewed with caution.
Spin-statistics matter for the intensities. The nuclear spin-weight ratio is 5 : 3 for ortho-c-C₅H₅N : para-c-C₅H₅N. The ortho states are described by K_a even, the para states by K_a odd.
The dipole moment was taken from (3).