Knowledge Bank

Accurate knowledge of collision-induced line shifts is required at the relevant atmospheric temperatures in the analysis of the observed $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CH4$ spectra of the atmospheres of the major planets, the Saturnian satellite Titan, and Earth, in addition to intensity and line width data. The appropriate temperatures fall in the range between 90 and 288 K and the relevant perturbers are $H2,He,N2$, and air. Using separate absorption cells for the reference and sample gases and placing them in series, we have been able to measure the pressure-induced shifts of the R(4) and R(7) multiplets located between 1330 and $1350cm-1$ in the $\nu 4$-fundamental of $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CH4$ at several temperatures between 100 and 296 K using a tunable diode laser. The temperature dependence of the shifts is presented for collisions of $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CH4$ with $H2,He,Ar,N2,O2$ and air. The experiments have also yielded data on the intensities and collision-broadened half-widths at the various temperatures. The different variation with temperature of the line width and the line shift for each line measured is discussed.