Please note: With respect to the initial entry of March 2012, values of Q and g_up were adjusted to be compatible with the 2nd ground state entry. In addition, intensities were corrected. The version number has been retained.
The transition frequencies were taken from
(1) M. Hutchinson, H. W. Kroto, and D. R. M. Walton, 1980, J. Mol. Spectrosc. 82, 394 and, more extensively, from
(2) K. M. T. Yamada, C. Degli Esposti, P. Botschwina, P. Förster, L. Bizzocchi, S. Thorwirth, and G. Winnewisser, 2004, Astron. Astrophys. 425, 767.
The entry has been created using Pickett's SPCAT. It mimicks the Hamiltonian in (2), and the parameters used are essentially identical. State number 0 refers to l = 0⁺, state number 1 to l = 0^–, and state number 2 to l = 2. The calculation should be reliable throughout.
The partition function DOES take into account now the hyperfine splitting, but no vibrational contributions !
Vibrational correction factors for a posteriori corrections have been derived for the main isotopolog in the harmonic approximation.
The vibrational energy is from a quantum-chemical calculation in (2). The dipole moment was assumed to be the same as that of the ground vibrational state, see e075503.cat.