Fourier transforms of the far infra-red pressure induced absorption bands in O2, CO2, and (CN)2 gases are compared with theoretical expressions derived from Î J= 2 and Î J= 4 (quadrupole and hexadecapole induced) line intensities. Satisfactory matching of theoretical and experimental normalised lineshapes displayed through the corresponding time domain functions, is obtained for O2 and CO2, but not for (CN)2. Reasons for these findings are discussed.