Analysis of the rotationally-resolved 3.3 µm region of C2H4 in natural isotopic abundance

Abstract

Ethylene (or ethene) is a natural gas compound present in our atmosphere but also in the atmospheres of outer solar system planets such as Jupiter, Saturn, Uranus, Neptune and Saturn's moon Titan. However, a better knowledge of spectroscopic parameters is needed for this molecule in order to detect its presence and/or to derive its accurate concentration. We present here a detailed analysis and modeling of the strongly absorbing ν9 and ν11 fundamental bands in the 3.3 µm region. Due to the complexity of the observed spectrum, we have built a polyad scheme taking into account some fundamental bands previously analyzed thanks to the tensorial formalism developed in Dijon for asymmetric-top molecules. A four polyad system has been settled and the last P3 polyad contains four vibrational states: ν9, ν11, ν2+ν12 and 2ν10+ν12. A first frequency analysis has been performed, leading to 3328 assignments with a root mean square of 5.927 ×10−3cm−1 and a standard deviation of 1.965 using 88 adjusted parameters, and we have also adjusted line intensities of 2190 lines by adjusting 14 parameters with an overall Root-Mean-Square (RMS) deviation of about 3.77%. A new linelist of calculated lines in the 2900−3300 cm−1 region has been added to the ECaSDa and we plan to integrate it to the HITRAN database.