- 1Institute of Materials Chemistry, TU Wien, Getreidemarkt 9/165, 1060 Vienna, Austria (dennis.dinu@tuwien.ac.at)
- 2Institute of Physical Chemistry, University of Innsbruck, Innrain 52c, 6020 Innsbruck, Austria
- 3Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 80, 6020 Innsbruck, Austria
- 4Chair of Theoretical Biophysics - Biomolecular Dynamics, TUM Munich, Ernst-Otto-Fischer-Straße 8, 85748 Garching, Germany
We have demonstrated that the combination of matrix isolation infrared (MI-IR) spectroscopy and vibration configuration interaction (VCI) calculations [1-3] is a feasible approach [4] to accurately assign and interpret IR spectra of single molecules, such as water [5], fluoroethane [6], carbon dioxide and methane [7].
Relying on our integral experimental-computational methodology for IR spectroscopy, we investigated carbon dioxide dimerization [8], including MI-IR spectroscopy of carbon dioxide monomers CO2 and dimers (CO2)2 trapped in neon and air. Based on our VCI calculations accounting for mode-coupling and anharmonicity, we identify additional IR-active bands in the MI-IR spectra due to the (CO2)2 dimer. In a systematic carbon dioxide mixing ratio study using neon matrices, we observe a significant fraction of the dimer at mixing ratios above 300 ppm, with a steep increase up to 1000 ppm. In neon matrix, the dimer increases the IR absorbance by about 15% at 400 ppm compared to the monomer absorbance alone. This suggests a high fraction of the (CO2)2 dimer in our matrix experiments.
In atmospheric conditions, such increased absorbance would significantly amplify radiative forcings and, thus, greenhouse warming. In the context of planetary atmospheres, our results improve our understanding of the greenhouse effect for planets of relatively thick CO2 atmospheres, such as Venus, where a significant fraction of the (CO2)2 dimer can be expected. There, the necessity of including the mid-IR absorption by stable (CO2)2 dimers in databases used for modeling radiative forcing, such as HITRAN, arises.
References
[1] G. Rauhut, JCP, 121, 19 (2004)
[2] M. Neff et al, JCP, 131, 12 (2009)
[3] H. J. Werner et al, JCP, 152, 14, (2020)
[4] D. F. Dinu et al, TCA, 139, 12, (2020)
[5] D. F. Dinu et al, JPCA, 123, 38 (2019)
[6] D. F. Dinu et al, JMS, 367, (2019)
[7] D. F. Dinu et al, PCCP, 22, 32 (2020)
[8] D. F. Dinu et al, JPCA, 126, 19, (2022)
How to cite: Dinu, D. F., Bartl, P., Quoika, P. K., Podewitz, M., Liedl, K. R., Grothe, H., and Loerting, T.: Increase of radiative forcing through mid-IR absorption by stable CO2 dimers? , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15992, https://doi.org/10.5194/egusphere-egu25-15992, 2025.
