Collision-induced absorption in ethylene in the microwave and far-infrared regions

Abstract

The collision-induced rotation–translation spectrum of gaseous ethylene has been measured at 295 K over a density range from 3.7 to 23.9 amagat in the 40–360 cm−1 region and at densities up to 50 amagat at 2.3 cm−1 and at 29.6 cm−1. The measurements were made using a Fourier transform spectrometer, an HCN laser, and a microwave cavity technique. Two spectral moments of the observed spectrum have been determined and used in a recently developed theory to provide values for the components of the quadrupole tensor of ethylene: Qxx = −3.54 × 10−26, Qyy = 1.77 × 10−26, Qzz = 1.77 × 10−26 esu. These values are compared with those obtained by other workers using different methods. The z direction is along the C–C axis, the y direction is in the plane of the molecule, and the x axis is perpendicular to the plane of the molecule.