The Dunham fit follows largely
(1) R. H. Petrmichl, K. A. Peterson, and R. C. Woods, 1988, J. Chem. Phys. 89, 5454.
Rovibrational data were also included. These were taken from
(2) Y. Akayama, K. Tanaka, and T. Tanaka, 1989, Chem. Phys. Lett. 155, 15.
The transition dipole moment was taken from a quantum-chemical calculation by
(3) K. A. Peterson, R. C. Woods, P. Rosmus, and H.-J. Werner, 1990, J. Chem. Phys. 93, 1889.
Transition frequencies should be reliable up to J = 30, possibly higher.
The partition function takes excited vibrational states into account.