Cyanamide tunnels between two equivalent positions, just as ammonia does. Details of the data set were described by
(1) A. Coutens, O. Zakharenko, F. Lewen, J. K. Jørgensen, S. Schlemmer, and H. S. P. Müller, 2019, Astron. Astrophys., 623, Art. No. A93.
Most of the experimental data within each tunneling state were taken from that work. Additional data are mostly from
(2) A. Krasnicki, Z. Kisiel, W. Jabs, B. P. Winnewisser, and M. Winnewisser, 2011, J. Mol. Spectrosc., 267, 144.
Few low frequency transitions are from
(3) R. D. Brown, P. D. Godfrey, and B. Kleibömer, 1985, J. Mol. Spectrosc., 114, 257;
and from
(4) J. K. Tyler, J. Sheridan, and C. C. Costain, 1972, J. Mol. Spectrosc., 43, 248.
Several parameters were kept fixed to parameters from a slightly rearranged parameter set of the main isotopolog as described in (1).
Since no c-type transitions between the two tunneling states have been published, these transitions cannot be predicted reliably at present, and their predictions have been omitted. Predictions should be viewed with caution once the predicted uncertainties exceed 0.2 MHz.
There are ortho and para states in cyanamide with a ratio of 3 : 1. The ortho states are described by K_a odd and even for the lower and upper tunneling component, respectively. Since cyanamide appears to be a hot core molecule, separate consideration of ortho and para states is not needed.
The dipole moment components were assumed to agree with those of the main isotopolog taken from (3).