Measured and simulated absorption of CO2 at high pressure and temperature: a new tool for remote sensing instruments

Here we present a comparison between measured and calculated absorption of CO2 gas at extreme conditions as found in the deep Venusian atmosphere. In addition, we describe a new tool to reproduce the absorption of CO2 with state of the art theory, in order to support remote sensing studies by instrumentation on orbiting spacecraft. Gas transmittance spectra have been recorded by a Fourier Transform InfraRed (FT-IR) spectrometer covering a wide spectral range, from 350 to 25000 cm-1 (0.4 to 29 ?m) with a spectral resolution from 10 to 0.07 cm-1. A special customized gas cell, certified to support pressures up to 350 bar and temperatures up to 300° C, has been integrated inside a compartment of the interferometer. A large number of spectra has been recorded on a pressuretemperature grid from 1 to 30 bar and 298 to 600 K. Our experimental spectra have been compared with synthetic spectra obtained by a software that takes into account line-mixing due to inter-molecular collisions. Inclusion of the line mixing, which is depending on the molecular density, produces spectra which differ substantially from those produced by simpler models, (such as ARS [3]) using a Voigt profile and neglecting line mixing, in particular for the high pressure and temperature conditions present in the Venus' atmosphere.