Figure 1. Part of the fundamental band of the CO2 dimer for (12C16O2)2, (13C16O2)2, and 12C16O2–13C16O2. An analogous range is covered for each isotopomer, but this is not so obvious since the nuclear spin statistics are different. The asterisks mark lines that are partly or entirely due to the He–CO2 complex. The simulations use parameters from Table 2, an effective rotational temperature of 3 K, and an assumed Gaussian linewidth of 0.0017 cm-1.