Line strength and halfwidth measurements from far infrared absorption spectra: Carbon monoxide

A method for deriving Lorentzian line shape parameters (line strengths and halfwidths) from absorption spectra taken at two different path lengths is discussed. Far i.r. absorption spectra of carbon monoxide are analysed to yield line strengths and halfwidths for the rotational transitions J″ = 3 through J>″ = 9. Experimental errors are discussed, and the value for the dipole moment derived from the line strengths, 0·108±0·005 D, is in agreement with the microwave value within experimental uncertainty. The Lorentzian halfwidths are compared, where appropriate, with two recent determinations of these quantities. Lorentzian halfwidths are also derived from absorption spectra taken at long path length using theoretical line strengths based upon μ_co = 0·112D.