HCNH+
Iminomethylium, protonated HCN, X 1Σ+
Species tag 028504
Version2*
Date of EntryDec. 2007
ContributorH. S. P. Müller

The experimental data was taken from
(1) M. Araki, H. Ozeki, and S. Saito, 1998, Astrophys. J. 496, L53.
With respect to the May 2001 entry, higher J data were used in the fit. They were published by
(2) T. Amano, K. Hashimoto, and T. Hirao, 2006, J. Mol. Struct. 795, 190.
The resulting fit was not satisfactory, even with the inclusion of the sextic centrifugal distortion constant H which appeared to be too big. Several trial fits indicated that it would be best to omit the J" = 2 and 5 lines from the fit. Predictions should be reliable up to about 1.3 THz.
With respect to the Aug 2006 entry, an H value was used in the fit. It was taken from
(3) P. Botschwina, 1986, Chem. Phys. Lett. 124, 382.
Note: The 14N hyperfine splitting can be resolved for very low values of J. Therefore, a separate hyperfine calculation is provided up to J" = 2. The predictions are based on astronomical observations described in
(4) L. M. Ziurys, A. J. Apponi, and J. T. Yoder, 1992, Astrophys. J. 397, L123.
The hyperfine structure has not been considered in the calculation of the partition function; all values have to be multiplied with 3 if hyperfine structure is taken into account !
Note: The version number has be retained.
The dipole moment is from an ab initio calculation in (3).

Lines Listed50
Frequency / GHz< 3682
Max. J50
log STR0-7.0
log STR1-8.5
Isotope Corr.-0.0
Egy / cm–10.0
 µa / D0.29
 µb / D 
 µc / D 
 A / MHz 
 B / MHz37055.75
 C / MHz 
 Q(300.0)169.0989
 Q(225.0)126.8938
 Q(150.0)84.6982
 Q(75.00)42.5123
 Q(37.50)21.4241
 Q(18.75)10.8833
 Q(9.375)5.6181
detected in ISM/CSMyes


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