Reaction and electronic excitation in crossed-beams collisions of low-energy O(3P) atoms with H2O and CO2

Collisions of low-energy (5--20 eV), ground-state oxygen atoms with H2O and CO2 in a crossed-beams geometry lead to chemical reaction in the case of H2O to produce OH (A2Σ+→X2Π) emissions; and to inelastic electronic excitation in the case of CO2 to produce the CO2 (A 1B2→X 1A1) flame bands. Species identifications are made through known wavelengths and emission intensities in the range 300--400 nm. The measured difference in threshold energies for the two processes confirms the channels involved. These are the first measurements in this energy range of optical emissions through collisions of fast neutral species