Examples of ¹²CO (dashed lines) and ¹³CO (solid lines) ﹩J=3\rightarrow 2﹩ spectra. (a) A typical pair of spectra located at (4^{﹩\arcmin﹩}, 0^{﹩\arcmin﹩}) showing similar ¹²CO/¹³CO ﹩J=3\rightarrow 2﹩ line ratios in the two velocity components. (b) Spectra at (2^{﹩\arcmin﹩}, 0^{﹩\arcmin﹩}) showing possible ¹²CO self absorption. (c) Spectra at (2^{﹩\arcmin﹩}, −12^{﹩\arcmin﹩}) near the south edge of the cloud showing different ¹²CO/¹³CO ﹩J=3\rightarrow 2﹩ line ratios in the different velocity components, as well as ¹²CO self‐absorption in the higher velocity component. (d) Spectra at (−2^{﹩\arcmin﹩}, 8^{﹩\arcmin﹩}) in M17 North showing strong ¹²CO but very weak ¹³CO. (e) Spectra of the photon‐dominated region M17 SW showing very complex emission structure, including possible ¹²CO self absorption at ~21 km s⁻¹. Note the expanded vertical scale for this panel.