Ultraviolet spectroscopy of pressurized and supercritical carbon dioxide
Open Access
- 25 May 2021
- journal article
- research article
- Published by Springer Science and Business Media LLC in Communications Chemistry
- Vol. 4 (1), 1-9
- https://doi.org/10.1038/s42004-021-00516-z
Abstract
Carbon dioxide (CO2) is prevalent in planetary atmospheres and sees use in a variety of industrial applications. Despite its ubiquitous nature, its photochemistry remains poorly understood. In this work we explore the density dependence of pressurized and supercritical CO2 electronic absorption spectra by vacuum ultraviolet spectroscopy over the wavelength range 1455-2000 Å. We show that the lowest absorption band transition energy is unaffected by a density increase up to and beyond the thermodynamic critical point (137 bar, 308 K). However, the diffuse vibrational structure inherent to the spectrum gradually decreases in magnitude. This effect cannot be explained solely by collisional broadening and/or dimerization. We suggest that at high densities close proximity of neighboring CO2 molecules with a variety of orientations perturbs the multiple monomer electronic state potential energy surfaces, facilitating coupling between binding and dissociative states. We estimate a critical radius of ~4.1 Å necessary to cause such perturbations.Keywords
Funding Information
- Research Corporation for Science Advancement (CCSA 7693)
- National Science Foundation (RUI 0809467)
- DOE | SC | Basic Energy Sciences (DE-FC02-04ER15533)
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