A combined fit of all available data of all isotopic species has been carried out; details are available in
(1) H. S. P. Müller, 2010, Astron. Astrophys. 514, Art. No. L6.
The J" = 0 transition frequencies of CH⁺, ¹³CH⁺, and CD⁺, were reported by
(2) T. Amano, 2010, Astrophys. J. 716, L1.
Additional rovibrational transitions between the electronic X and A states of four isotopologs as reported in (1) were also used in the fit. The CH⁺ data were taken from
(3) A. Carrington and D. A. Ramsay, 1982, Phys. Scr. 25, 272;
and from
(4) R. Hakalla, R. Kepa, W. Szajna, and M. Zachwieja, 2006, Eur. Phys. J. D 38, 481.
¹³CH⁺, CD⁺, and ¹³CD⁺ data were taken from
(5) Z. Bembenek, 1997, J. Mol. Spectrosc. 181, 136;
from
(6) Z. Bembenek, H. Cisak, R. Kepa, 1987, J. Phys. B 20, 6197;
and from
(7) Z. Bembenek, 1997, J. Mol. Spectrosc. 182, 439;
respectively.
Predictions should be viewed with considerable caution for transitions beyond J" = 10.
The dipole moment was taken from an ab initio calculation by
(8) B. Follmeg, P. Rosmus, and H.-J. Werner, 1987, Chem. Phys. Lett. 136, 562.