Absorption coefficient measurements for trace amounts of methane are reported, in a 1-atm argon balance, at seventeen deuterium-fluoride (DF) laser line frequencies. An optoacoustic detector (spectrophone) operating within the DF laser optical cavity yielded a minimum detectable absorption of 0.007 km-1 (7 × 10-8 cm-1) for a 10:1 SNR. Results are compared with previous measurements and with calculated absorption coefficients obtained using the AFGL atmospheric absorption parameter compilations. A 2.5-fold increase in agreement results when the 1980 AFGL methane parameters are used instead of the 1978 parameters.
D. H. Leslie and G. L. Trusty, "Measurements of DF laser absorption by methane using an intracavity spectrophone," Appl. Opt. 20, 1941-1947 (1981)