Knowledge Bank

The self-broadening coefficients and the $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C/12C$ isotope intensity ratios for several tetrahedral multiplets in the $\nu 3$-band of methane have been measured with a difference-frequency laser spectrometer, The instrumental resolution of $\sim 10-4$ $cm-1$ permits undistorted spectral profiles to be recorded from the low pressure Doppler limit to the broadened atmospheric pressure range where serious overlap of the multiplet components occurs. The data have been curve-resolved by computer fitting with Gaussian and Lorentzian lineshapes. The $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH4/12CH4$ intensity ratio is determined to be $0.99\pm 0.02$ as measured from the integrated line strengths of corresponding transitions for the two isotopes.