Density Dependence Of Spectral Detail In Pressurized And Supercritical Carbon Dioxide Electronic Absorption Spectra

Marin, Timothy W

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https://hdl.handle.net/2142/111557 Copy

Description

Title

Density Dependence Of Spectral Detail In Pressurized And Supercritical Carbon Dioxide Electronic Absorption Spectra

Author(s)

Marin, Timothy W

Contributor(s)

Janik, Ireneusz

Issue Date

2021-06-22

Keyword(s)

Comparing theory and experiment

Abstract

The density dependence of pressurized and supercritical carbon dioxide (CO$_{2}$) electronic absorption spectra was explored by vacuum ultraviolet (VUV) spectroscopy over the wavelength range 1455-2000 \AA. The peak energy position of the lowest absorption band of gaseous CO$_{2}$ does not change upon pressurizing up to and beyond the thermodynamic critical point (137 bar, 308 K). Upon increase of density, the known diffuse vibrational structure inherent to the VUV absorption spectrum of gaseous CO$_{2}$ gradually diminishes in magnitude and nearly disappears upon reaching a density of 0.767 g cm$^{-3}$. This loss of spectral detail cannot be explained solely by collisional broadening and/or dimerization. We suggest that perturbation of the monomer potential energy surfaces belonging to multiple upper electronic states leads to increased coupling between binding and dissociative states. This perturbation is caused by the near proximity of CO$_{2}$ molecules at high densities and a variety of orientations without the need for equilibrated dimers, and in turn gives rise to the observed spectral changes. Based on a high-quality CO$_{2}$ dimer potential energy surface, we estimate a critical radius of 4.1 +/- 0.2 \AA{ } between molecules necessary to cause such perturbations.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Permalink

http://hdl.handle.net/2142/111557

DOI

10.15278/isms.2021.TE11

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