Temperature‐dependent photoabsorption cross sections in the VUV‐UV region: Ethylene

Abstract

Using synchrotron radiation as a continuum light source, we have measured the absolute photoabsorption cross sections of ethylene (C2H4) in the region between 118 nm and 192 nm with a spectral bandwidth (full width at half maximum) of 0.06 nm and at five different temperatures: 370 K, 330 K, 295 K, 200 K, and 140 K. Significant temperature effects are observed in several spectral regions, including the threshold absorption region. From the Pc,370K curve we are able to identify and assign several hot bands. When the gas temperature decreases from 370 K to 140 K, the cross sections of the hot bands in the 190 nm region decrease by an order of magnitude. The line shapes of the Pc,T exhibit characteristic symmetric and asymmetric peaks, as well as the first derivative‐like and second derivative‐like curves associated with various absorption features. The results obtained in the present work provide the required data to the planetary atmospheres community and may have an important contribution to our understanding of the atmospheres of giant planets.