Trihydrogen cation; di-deuterium isotopolog
Species tag 005501
Date of EntryJan. 2018
ContributorH. S. P. Müller

Both H3+ and D3+ do not have a permanent dipole moment because of symmetry. In contrast, both H2D+ and HD2+ have sizable dipole momenta.
The first entry from April 2004, modified Aug. 2005, and the second entry from Feb. 2012 have been modified considerably. Details are given in
(1) P. Jusko, M. Töpfer, Holger S.P. Müller, P. N. Ghosh, S. Schlemmer, and O. Asvany, 2017, J. Mol. Spectrosc., 332, 33.
Please note that the parameter set is slightly different in the present compilation because of one addition line from (4); X21 was omitted and Y20 was used instead. Multiple transition frequencies were retained as long as they were compatible with each other.
The J = 1 – 0 transition of ortho-HD2+ was taken from
(2) O. Asvany, O. Ricken, H. S. P. Müller, M. C. Wiedner, T. F. Giesen, and S. Schlemmer, 2008, Phys. Rev. Lett., 100, Art. No. 233004.
The J = 1 – 1 transition of para-HD2+ was taken from
(3) T. Hirao and T. Amano, 2003, Astrophys. J., 597, L85.
Five additional frequencies with microwave accuracy were reported by
(4) S. Yu, J. C. Pearson, T. Amano, and F. Matsushima, 2017, J. Mol. Spectrosc., 332, 33.
All except one were used in (1). Three transition frequencies from (2), (3), and one from (4) were remeasured in (1) with much greater accuracy. One additional transition frequency of ortho-HD2+ was reported by
(5) D. A. Jennings, C. Demuynck, M. Banek, and K. M. Evenson, private communication in
O. L. Polyansky and A. R. W. McKellar, 1990, J. Chem. Phys., 92, 4039
Two infrared ground state combination differences (GSCDs) with nearly microwave accuracy were taken from
(6) P. Jusko, C. Konietzko, S. Schlemmer, O. and Asvany, 2016, J. Mol. Spectrosc., 319, 55.
Additional less accurate GSCDs reported in (3) were also used in the fit.
Note: uncertainties of 999.9999 MHz or 0.03336 cm–1 are the largest ones displayed ! All predictions should be viewed with caution because of the small data set.
The ab initio dipole moment was mentioned by
(7) S. C. Foster, A. R. W. McKellar, and J. K. G. Watson, 1986, J. Chem. Phys., 85, 664.
At low temperatures, it may be necessary to discern between ortho-HD2+ and para-HD2+. The ortho and para states are described by Ka + Kc even and odd, respectively. The nuclear spin-weight ratio is 2 : 1 for ortho-HD2+ : para-HD2+. The JKaKc = 101 is the lowest para state. It is 34.9184 cm–1 above ground.
Separate para and ortho predictions are available up to J = 3 and Ka = 3 along with separate para and ortho partition function values.

Lines Listed163
Frequency / GHz< 15436
Max. J11
log STR0-6.0
log STR1-5.3
Isotope Corr.-7.879
Egy / (cm–1)0.0
 µa / D 
 µb / D0.486
 µc / D 
 A / MHz1085205.
 B / MHz655725.
 C / MHz391794.
detected in ISM/CSMyes

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