Photoion--photoelectron coincidence study of (CO)/sub 2/ and (CO)/sub 3/
The photoion--photoelectron coincidence (PIPECO) spectra for (CO)/sup +//sub 2/ in the wavelength region of 620--990 A have been obtained at different nozzle stagnation pressures (P/sub 0/). The ionization energy for (CO)/sub 2/ to CO/sup +/(X)xCO is determined to be approx. <12.73 +- 0.05 eV (974 +- 4 A), indicating that CO/sup +/(X)xCO is bound by more than 1.29 eV. The PIPECO measurements also provide evidence that CO/sup +/(A-italic-tilde,B-italic-tilde)xCO are bound with dissociation energies >0.3 eV. At P/sub 0/less than or equal to200 Torr and a nozzle temperature (T) of 120 K, nozzle expansion conditions which minimize the formation of (CO)/sub n/ (ngreater than or equal to3), the intensities for the CO/sup +/(A-italic-tilde,B-italic-tilde)xCO PIPECO bands are found to be negligibly small compared to that for the CO/sup +/(X)xCO PIPECO band. This observation supports the conclusion that the excited CO/sup +/(A-italic-tilde,B-italic-tilde)xCO ions are dissociative, with dissociation lifetimes<42 ..mu..s. This conclusion is contrary to that of the preliminary study which is based on the PIPECO spectrum for (CO)/sup +//sub 2/ measured at P/sub 0/ = 350 Torr and T = 120 K. Assuming that the radiative lifetimes of CO/sup +/(A-italic-tilde or B-italic-tilde) and CO/sup +/(A-italic-tilde or B-italic-tilde)xCO are identical, we estimate that the dissociation lifetimes for CO/sup +/(A-italic-tilde)xCO and CO/sup +/(B-italic-tilde)xCO are approx. <4 ..mu..s and approx. <50 ns, respectively.
- Research Organization:
- Ames Laboratory, U.S. Department of Energyand Department of Chemistry, Iowa State University, Ames, Iowa 50011
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 6085369
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 90:11; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTRA
ADDUCTS
BEAMS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
COINCIDENCE METHODS
COUNTING TECHNIQUES
DIMERS
DISSOCIATION
IONIZATION
MOLECULAR BEAMS
OXIDES
OXYGEN COMPOUNDS
PHOTOIONIZATION
SPECTRA