Product vibrational state distributions of thermal energy charge transfer reactions determined by laser-induced fluorescence in a flowing afterglow: Ar++CO→CO+(v=0–6)+Ar

The Ar++CO→CO+(v=0–6)+Ar charge transfer reaction is studied at thermal energy in a flowing afterglow and the vibrational state distribution is determined by laser-induced fluorescence on the CO+(A 2Π–X2Σ+) bands. The nascent vibrational state distribution is (0.06±0.04)v=0 :(0.07±0.02)v=1 :(0.09±0.02)v=2 :(0.15±0.03)v=3 :(0.21±0.03)v=4: (0.27±0.02)v=5 :(0.15±0.02)v=6. The rate constant for CO+(v=4) deactivation by CO is measured to be 6.0±2.5×10−10 cm3 s−1; the similarity of this rate constant to that for CO+(v=1) deactivation by CO (5.0±2.0×10−10 cm3 s−1) suggests that vibrational deactivation proceeds by a charge transfer mechanism. The Ar++CO reaction is described as proceeding via a bent ArCO+ intermediate that forms in a side-on attack. Vibrational excitation may then result from delocalization of the bonding electron density of CO and the corresponding dynamical changes in the CO bond length in the intermediate.