Chloronium, X 1A1
Species tag 037504
Date of EntryMar. 2015
ContributorH. S. P. Müller

Chloronium, also known as protonated HCl, is isoelectronic to H2S. The experimental lines are from
(1) M. Araki, T. Furuya, and S. Saito, 2001, J. Mol. Spectrosc. 210, 132.
The uncertainties are assumed values and should be viewed with some caution. Overlapping lines have not been merged.
Also used in the fit were infrared transitions from
(2) K. Kawaguchi and E. Hirota, 1986, J. Chem. Phys. 85, 6910;
and from
(3) S. K. Lee, T. Amano, K. Kawaguchi, and M. Oldani, 1988, J. Mol. Spectrosc. 130, 1.
With respect to the Nov. 2009 entry, two very weak HFS components have been added for the transition 21,2 – 10,1 near 782 GHz. The version number has been retained. Thus far, only ground state transitions have been observed. Therefore, predictions should be sufficient for all astronomical purposes. More generally, predictions with uncertainties much larger than 1 MHz should be viewed with caution.
The dipole moment is from an ab initio calculation by
(4) H. S. P. Müller; 2008, unpublished.
At low temperatures, it may be necessary to discern between ortho-H2Cl+ and para-H2Cl+. The ortho and para states are described by Ka + Kc being odd and even, respectively. The nuclear spin-weights are 3 and 1 for ortho-H2Cl+ and para-H2Cl+, respectively. The JKaKc = 101, F = 1.5 is the lowest ortho state. It is 14.0630 cm–1 above ground.
May 2010: separate para and ortho predictions are available up to about 100 cm–1 along with separate para and ortho partition function values. Note: the spin-weight of 3 for the separate ortho predictions has been eliminated.

Lines Listed600
Frequency / GHz< 4000
Max. J13
log STR0-5.0
log STR1-3.5
Isotope Corr.-0.121
Egy / (cm–1)0.0
 µa / D 
 µb / D1.89
 µc / D 
 A / MHz337352.3
 B / MHz273587.8
 C / MHz148100.7
detected in ISM/CSMyes

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