@article{McCarthy15082006,
author = {McCarthy, M. C. and Mohamed, S. and Brown, J. M. and Thaddeus, P.}, 
title = {Detection of low-frequency lambda-doublet transitions of the free 12CH and 13CH radicals},
volume = {103}, 
number = {33}, 
pages = {12263-12268}, 
year = {2006}, 
doi = {10.1073/pnas.0601746103}, 
abstract ={By Fourier transform microwave spectroscopy, lambda-doubling transitions of 12CH and 13CH in the lowest rotational levels of the X
               2∏1/2 ground state have been directly detected, which has not been done previously. For both radicals, hyperfine-split lines have been measured to an accuracy of better than 1 ppm between 3 and 15 GHz, an improvement of at least 2 orders of magnitude over previous laboratory data. The measured frequencies have been combined with all previous data for CH and 13CH in the v = 0 level of the X
               2∏ electronic state to determine improved hyperfine parameters. The production of CH from various gases also has been studied and, with methanol, the yield of CH relative to OH. Astronomical studies of CH in higher rotational levels and 13CH can now be undertaken on the basis of the present work.}, 
URL = {http://www.pnas.org/content/103/33/12263.abstract}, 
eprint = {http://www.pnas.org/content/103/33/12263.full.pdf}, 
journal = {Proceedings of the National Academy of Sciences} 
}