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We have studied the excitation of metastable O(1D) following dissociative excitation of CO2 in the electron impact energy range from threshold to 400 eV. A solid Ne matrix at ∼20 K forms the heart of the detector. This is sensitive to the metastable species through the formation of excited excimers (NeO*), The resultant excimer radiation is readily detected, providing a means of measuring the production of the metastables. Using a pulsed electron beam and time-of-flight techniques, we have measured the O(1D) kinetic energy spectrum and its relative production cross sections as a function of electron impact energy. Threshold energy data are used to gain information about the excitation channels involved. In addition, an emission excitation function for the red photons, emitted in coincidence with the exciting electron pulse, has been measured in the 0–400 eV energy range.

Dissociative excitation of SO2 by electron impact to produce excited oxygen fragments, in particular O (1S), has been studied in the energy range from threshold to 400 eV. Three processes leading to O (1S) production have been identified and the positions of the relevant repulsive states of SO2 in the Franck–Condon region have been determined. The multiplicities and symmetry characteristics of two of these states have also been established. The absolute cross section for production of O (1S) by all channels is measured to be 2.2 x 10-18 cm2 at 150 eV. The relative cross section for production of O (3p 3P and 3p 5P) from threshold to 400 eV has also been measured. The existence of a hitherto unidentified triplet state of SO2 that emits in the near infra red has been established. PACS No.: 34.80Gs

A variety of techniques have been applied to study the interaction of electrons with beams of CO2 molecules which are heavily clustered. Fragmentation of the clusters is monitored by detecting excited fragments directly or via the vacuum ultra-violet photons which they emit as they decay. The evidence obtained points to the conclusion that the excited molecules are essentially decoupled from the clusters during fragmentation. The shape of the excitation functions are indicative of the dominance of optically allowed processes in the initial interaction.PACS Nos.: 36.40+d and 34.80.GS