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http://hdl.handle.net/20.500.12386/28878
Titolo: | Collisional Induced Absorption (CIA) bands measured in the IR spectral range | Autori: | STEFANI, STEFANIA PICCIONI, GIUSEPPE Snels, M. Adriani, A. Grassi, D. |
Data pubblicazione: | 2016 | Rivista: | MEMORIE DELLA SOCIETA ASTRONOMICA ITALIANA | Numero: | 87 | Da pagina:: | 208 | Abstract: | In this work we present two experimental setup able to characterize the optical properties of gases, in particular CO_2 and H_2, at typically planetary conditions. The apparatus consists of a Fourier Transform InfraRed (FT-IT) interferometer able to work in a wide spectral range, from 350 to 25000 cm<SUP>-1</SUP> (0.4 to 29 mu m ) with a relatively high spectral resolution, from 10 to 0.07 cm<SUP>-1</SUP>. Two dedicated gas cells have been integrated with the FT-IR. The first, called High Pressure High Temperature (HP-HT), can support pressures up to 300 bar, temperatures up to 300<SUP>o</SUP>C and is characterized by an optical path of 2 cm. The second one, a Multi Pass (MP) absorption gas cell, is designed to have a variable optical path, from 2.5 to 30 m, can be heated up to 200<SUP>o</SUP> and operate at pressures up to 10 bar. In this paper, measurements of Collision-Induced Absorption (CIA) bands in carbon dioxide and hydrogen recorded in the InfraRed spectral range will be presented. In principle, linear symmetric molecules such as CO_2 and H_2 possess no dipole moment, but, even when the pressure is only a few bar, we have observed the Collisional Induced Absorption (CIA) bands. This absorption results from a short-time collisional interaction between molecules. The band integrated intensity shows a quadratic dependence versus density opposed to the absorption by isolated molecules, which follows Beer's law \citep{Beer's}. This behaviour suggests an absorption by pairs rather than by individual molecules. The bands integrated intensities show a linear dependence vs square density according to \citep {CIA Shape} and \citep{CIA posi}. For what concerns the H_2 CIA bands, a preliminary comparison between simulated data obtained with the model described in \citep{CIA H2}and measured, shows a good agreement. These processes are very relevant in the dense atmospheres of planets, such as those of Venus and Jupiter and also in extrasolar planets. A detailed knowledge of these contributions is very important to include this effect in the radiative transfer calculations. | URI: | http://hdl.handle.net/20.500.12386/28878 | URL: | http://sait.oat.ts.astro.it/MSAIt870116/index.html | ISSN: | 0037-8720 | Bibcode ADS: | 2016MmSAI..87..208S | Fulltext: | open |
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