L. Siller et al., Electron stimulated desorption from solid CO2 and a hydrogen containing CO2 matrix: A comparative study, J CHEM PHYS, 110(21), 1999, pp. 10554-10561
We have studied electron stimulated desorption of positive ions from simila
r to 15 monolayer (ML) film of pure solid CO2 adsorbed on polycrystalline P
t surface at similar to 40 K using incident electrons in the energy range 1
-31 eV. The positive ions O+, C+, CO+, CO2+, and O-2(+) were observed and t
heir threshold energies are discussed. Hydrogenation of the CO2 film was fo
und to reduce the O-2(+) production but the threshold remained the same as
for the pure CO2 matrix. After hydrogenation of the CO2 matrix additional i
ons-H+, H3O+, HCO+, and H2CO+-are observed. The formation of formaldehyde c
ations (with a threshold energy of 17+/-1.5 eV) in the hydrogenated CO2 mat
rix has been observed for the first time and is a product of electron stimu
lated ion-molecule reactions, possibly via a process analogue to the so-cal
led photosynthesis. These results could be relevant to a better understandi
ng of the atmosphere of Mars. (C) 1999 American Institute of Physics. [S002
1-9606(99)70821-4].