C5N
Cyanobutadiynylide ion, X 1Σ+
Species tag 074513
Version1*
Date of EntryOct. 2008
ContributorH. S. P. Müller

The cyanobutadiynylide ion has been detected very recently in the circumstellar shell of IRC +10216. Even though no laboratory data are available at present, very accurate ab initio calculations, see below, provide very reliable spectroscopic parameter. Combined with the chemistry in that source, the assignment of the C5N appears to be rather secure; see also the Molecules in Space section. Rest frequencies were taken from
(1) J. Cernicharo, M. Guélin, M. Agúndez, M. C. McCarthy, and P. Thaddeus, 2008, Astrophys. J., accepted.
U33332.3, reported by
(2) K. Kawaguchi, Y. Kasai, S.-I. Ishikawa, and N. Kaifu, 1995, Publ. Astron. Soc. Japan 47, 853;
is, at least in part, due to C5N. Therefore, this line was also used in the fit.
The 14N hyperfine splitting may be be resolvable for low values of J. Therefore, a separate hyperfine calculation is provided up to J" = 4. The eQq value was taken from C3N; this is probably a good, but not perfect assumption. The spin multiplicity gI of 3 for the 14N nucleus is NOT included in the partition function or in the upper state degeneracy gup of the general entries. The partition function values have to be multiplied by 3 if hyperfine splitting is taken into account.
The reported line uncertainties seem to be somewhat conservative; based on the fit results, they seem to be 2 σ values. The predictions are probably reliable up to 200, maybe even 300 GHz.
The dipole moment is from an ab initio calculation by
(3) P. Botschwina and R. Oswald, 2008, J. Chem. Phys. 129, Art. No. 044305.

Lines Listed191
Frequency / GHz< 530
Max. J191
log STR0-6.7
log STR1-3.7
Isotope Corr.-0.0250
Egy / cm–10.0
 µa / D5.23
 µb / D 
 µc / D 
 A / MHz 
 B / MHz1388.86
 C / MHz 
 Q(300.0)4502.0711
 Q(225.0)3376.4600
 Q(150.0)2250.9667
 Q(75.00)1125.5912
 Q(37.50)562.9476
 Q(18.75)281.6370
 Q(9.375)140.9846
detected in ISM/CSMyes


Database maintained by Holger S. P. Müller and Sven Thorwirth, programming by D. Roth and F. Schlöder