ON COLLISION-INDUCED ABSORPTION IN PURE $O_{2}, CO_{2}$, AND $CO_{2} - O_{2}$ MIXTURES.
Loading...
Date
2003
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The NIST high-pressure absorption cell coupled to a DA002 Fourier-transform spectrometer has been modified in order to extend the lower temperature range of the measurements. Measurements of collision-induced absorption (CIA) of pure $O_{2}$ and $CO_{2}$ as well as $CO_{2} - O_{2}$ mixtures have been recorded from room temperature down to $-80^{\circ} C$. The spectra of compressed $CO_{2}$ in the $\nu_{1} - 2 \nu_{2}$ infrared inactive Fermi dyad region consist of two anharmonically-coupled bands. Each of these bands includes a featureless CIA band on top of which is superimposed a distinctive $CO_{2}$ dimer band. These dimer bands increase in intensity with decreasing temperature but surprisingly persist up to room temperature. Spectra of mixtures of $CO_{2}$ and $O_{2}$ have also been obtained. As $CO_{2}$ is added to pure $O_{2}$ in the absorption cell, the intensity of the $O_{2}$ fundamental band grows rapidly. At higher $CO_{2}$ concentrations, the band narrows and unresolved ro-vibrational structure appears at the center. Its appearance indicates that a fairly strongly bound $O_{2}\ldots CO_{2}$ complex is formed. Attempts are presently underway to model the observed van der Waals complexes as well as the structureless CIA profiles. Binary absorption coefficients have been derived for all species studied at $0.25 cm^{-1}$ intervals over the range 1100 to $1800 cm^{-1}$.
Description
Author Institution: Optical Technology Division, NIST, Gaithersburg; General Physics Institute, Russian Academy of Sciences