The experimental lines are from
(1) S. Saito, K. Kawaguchi, S. Yamamoto, M. Ohishi, H. Suzuki, and N. Kaifu, 1987, Astrophys. J. 317, L115; and from
(2) F. J. Lovas, R. D. Suenram, T. Ogata, and S. Yamamoto, 1992, Astrophys. J. 399, 325.
Also included are two lines from
(3) S. Yamamoto, unpublished.
These are the N_J = 1₂ – 2₁ and 2₃ – 1₂ lines at 22344.0308 and 33751.3696 MHz with an estimated experimental uncertainty of 1.0 kHz.
Extrapolations to frequencies much higher than 300 GHz should be viewed with some caution.
The dipole moment is from an ab initio calculation from
(4) G. Pascoli, H. Lavendy, 1998, Int. J. Mass Spectrom 181, 11.