Far-infrared collision-induced absorption in some compressed gaseous polar molecules of atmospheric interest

The higher frequency part of the far-infrared pressure-induced absorption in gaseous polar molecules has its origin in binary collision-induced dipolar absorption. The lower frequency part of the band observed is due to the induced translational absorption. Detailed expressions for different possible contributions to the integrated intensities are reported for diatomics (CO, HCl), linear molecules (N₂O, OCS) and symmetric top molecules (halogenated methanes such as CF₃Cl, CF₃H). From these calculated expressions and the moderately low pressure FIR data, new values of the quadrupole moment of N₂O and CF₃Cl (|Θ|_N2O = 12.3 × 10^×40C.m², |Θ|_CF3Cl = 22.0 × 10^-40C.m²) are determined.