Knowledge Bank

Laser magnetic resonance spectra between 0 and 17 kG have been recorded and analyzed for $(J\prime -J\prime \prime )=(7/2-5/2),(5/2-3/2)$, and (3/2 - 1/2) transitions in the CH molecule, using the optically pumped far infrared lasers: $118.8\mu m(CH3OH),180.7\mu m(CD3OH),554.4\mu m(CH2CF2)561.3\mu m(DCOOD)$, and $567.9\mu m(CH2CHCl)$. Other transitions in CH were detected with the $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH3OH$ laser at 115.8, 149.3 and $203.6,\mu $m. The CH radical was generated in a low-pressure methane and atomic fluorine flame within the laser cavity. Analysis of the structure yields wave-numbers for the rotational transitions mentioned above of 84.3494, 55.3397, and $17.8376cm-1$, respectively. Combining results from the $MJ$ analysis with the $J=1/2$ A-doubling interval derived from radioastronomy measurements yields A-doubling values for the $J=3/2,5/2$, and 7/2 states of 0.0237, 0.1620, and $0.3759cm-1$, respectively. Both the rotational intervals and the A-doublings are in good agreement with earlier less precise optical results. Analysis of the hyperfine structure yields values for the Frosch and Foley hyperfine parameters of $a=+52,b=-74,c=+52$ and $d=+43.6$ MHz, in good agreement with recent ab initio estimates and radio-astronomy measurements.