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 dipole moment was derived 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 800 GHz, possibly higher.
The partition function takes excited vibrational states into account, but is not fully converged at 2000 K.