Translational energy spectroscopy of beams of C +( 2Pu) and C +( 4Pg) ions

Abstract

Beams of C + ions are made by electron impact on CO, CO 2 and CH 4 at 70 eV. Electronic transitions of these ions are observed using TES spectroscopy of the type developed by Illies and Bowers [Chem. Phys., 65 (1982) 281]. He, NO and O 2 collision gases were used to induce the electronic transitions. Only energy-loss transitions originating from C +( 2 P u) to other states in the doublet manifold were observed for He collision gas. For NO and O 2 an energy-loss transition assignable to C +( 2 P u) → C +( 4 P g) was also observed. The complementary superelastic transition C +( 4 P g) → C +( 2 P u) was also seen for NO and O 2 collision gases. All of the transitions observed were interpreted in terms of state symmetries of the quasi-molecule formed between C + and the collision gas, where “forbidden” crossings between curves of the same symmetry dominate. From the relative intensities of the C +( 2 P u) ⇌ C +( 4 P g) transitions it was possible to determine the fractional population of C +( 4 P g) in the ion beam. For 70 eV electron impact on CO a value of 16% was obtained and for CO 2 a value of 6.3%. The deactivation of C +( 4 P g) by CO was measured to be fast, 1±0.5 × 10 −9 cm 3 s −1. These results were compared with other results available in the literature.