Transitions between the spin-rotational levels of the 12 CH radical in the v = 1 level of the X 2 Π state have been studied by the technique of laser magnetic resonance at far-infrared wavelengths. The data have been combined with a measurement of lambda-doubling transition frequencies at 7 GHz to determine an improved set of molecular parameters for CH in the v = 1 level. The parameters provide information on the effects of vibrational excitation on the structural properties of CH. Accurate predictions of the transition frequencies between the low-lying levels of the radical in the absence of a magnetic field have also been made. Small inconsistencies in the least-squares fit of the laser magnetic resonance data prompted re-measurement of three far-infrared laser frequencies, the 122.5 μm line of CH 2 F 2 pumped by 9R(22), the 122.5 μm line of CH 2 F 2 pumped by 9P(8) and the 554.4 μm line of CH 2 CF 2 pumped by 10P(14). The new measurements differ by as much as 3.8 MHz from those made previously and are more accurate; they also remove the inconsistencies in the fit. The re-measured frequencies of the two 122.5 μm lines are identical within experimental error which suggests that the far-infrared lasing transition is the same, namely the r R 23 (32) transition in the v 9 =1 level of CH 2 F 2 . © 2007 Elsevier Inc. All rights reserved.
Jackson, M., Zink, L. R., McCarthy, M. C., Perez, L., & Brown, J. M. (2008). The far-infrared and microwave spectra of the CH radical in the v = 1 level of the X 2 Π state. Journal of Molecular Spectroscopy, 247(2), 128–139. https://doi.org/10.1016/j.jms.2007.11.001