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Photoionization of CO2 (ARPES)

Vibrational branching ratios and asymmetry parameters in the photoionization of CO2 in the region between 650 Å and 840 Å


A.C. Parr,1  J.B. West,2  M.R.F. King,2  K. Ueda,3  P.M. Dehmer,4  J.L. Dehmer,5  D.J. Schwab,6  A.M. Sansonetti,6  K. Olsen,6  and R.A. Dragoset6

1Sensor Science Division, NIST, Gaithersburg, MD 20899, USA
2Daresbury Laboratory, Warrington, WA4 4AD, UK
3Research Institute for Scientific Measurements, Tohoku University, Sendai 980, Japan
4Office of Basic Energy Science, U.S. Department of Energy, Germantown, MD 20874, USA
5National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22230, USA
6Physical Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA


Abstract

The vibrational branching ratios and asymmetry parameters for CO2 have been determined in the wavelength region of 650 Å to near the ionization onset at about 840 Å. The study was performed using synchrotron radiation from the Daresbury storage ring that was dispersed with a 5 m grating monochromator that afforded resolution of 0.1 Å to 0.2 Å. This resolution allowed the study of the branching ratios and asymmetry parameters with enough detail to see the changes in the parameters within the pronounced autoionization structure in CO2 in this wavelength region. While the electron spectrometer resolution was not sufficient to resolve the spin orbit and Renner-Teller splitting in the photoelectron spectra, we are able to fit the data with a model that identifies the major structure in terms of the symmetric stretch and elements of the asymmetric stretch and bending modes. A calculation of the expected relative vibrational excitations based upon the Franck-Condon principle clearly showed non-Franck-Condon behavior in some of the vibrational-electronic transitions.

Table of Contents

  1. Introduction
  2. Experimental Procedure
  3. Analysis of the Data
  4. Discussion
  5. References
  6. List of Figures
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