Dissociative and double photoionization of CO₂ from threshold to 90 Å

Behlen Laboratory of Physics University of Nebraska-Lincoln, NE 68588 , Lincoln.

Abstract

The molecular photoionization [Math], dissociative photoionization (CO⁺ O⁺ and C⁺) and double photoionization (CO²⁺ and C²⁺) cross sections for CO₂ have been measured from their onsets down to 90 A by using various combinations of mass spectrometers (a coincidence time of-flight mass spectrometer and a magnetic mass spectrometer) and light sources (synchrotron radiation, and glow and spark discharge). It Is concluded that the one broad peak and the three shoulders In the total absorption cross section curve between 640 and 90 A are caused completely by dissociative ionization processes. Several peaks observed In the cross section curve for the total fragmentation (CO⁺, O⁺ and C⁺) are compared with those in the photoelectron spectrum reported for CO₂. The accuracy of the present cross sections Is estimated to be about 10, 15 and 50 % for σ (CO₂) σ (CO⁺, O⁺ and C⁺) and σ (CO²⁺and C²⁺), respectively.

Résumé

Les sections efficaces de photionisation moléculaire (CO⁺), la photoionisation dissociative (CO⁺, O⁺, C⁺) et la photoionisation double (CO²⁺ et C²⁺) ont été mesurées pour le CO₂ du seuil jusqu'à 90 Å. Plusieurs combinaisons de spectromètres de masse et de sources d'excitation ont été utilisées. On conclut que les structures observées dans la section efficace d'absorption totale entre 640 et 90 Å sont dues entièrement à des processus d'ionisation dissociative. On compare les structures observées dans les sections efficaces pour la fragmentation totale (CO⁺, O⁺ et C⁺) aux spectres photoélectroniques de CO2. La précision des sections efficaces est de l'ordre de 10, 15 et 50 % respectivement pour σ (CO₂), σ (CO⁺, O⁺ et C⁺) et σ (CO₂ et C²⁺).