Photodissociation of the dimer ions Ar +2, Ne +2, and (CO 2) +2

Abstract

The tandem quadrupole photodissociation mass spectrometer has been used to study photodissociation reactions of Ar + 2, Ne + 2, and (CO 2) + 2. The cross sections for photodissociation of Ar + 2 exhibited a strong dependence on ion source pressure, varying from 2 × 10 −18cm 2 at 0.1 torr to 6 × 10 −19cm 2 at 0.5 torr. A large photodissociation cross section (2 × 10 −17cm 2 for the reaction (CO 2) + 2 → CO + 2+ CO 2 was observed at the red end of the visible spectrum (580–620 nm) suggesting that this may be an important reaction in CO 2 rich planetary ionspheres such as that of Mars.