Ion Recoil Following (2+1) REMPI of Nascent Atoms - The Effect on Nascent Velocity Distributions in Velocity Map Imaging

摘要

Velocity map imaging has achieved thus far a resolution at 1 eV kinetic energy release of approx 30 meV, thus 3% #DELTA#E/E. In order to further improve the resolution we need to look more critically at one of the assumptions in the imaging method - that the conversion of neutral fragments to ionic fragments using the standard REMPI technique does not significantly change the nascent velocity distribution of the neutral species. This is shown in the paper to be a questionable assumption in many cases. The effects of ion recoil due to the detection process in the photodissociation of HI and O_2 are predicted to fall in the 2-3% range for normal conditions in velocity map imaging. Recoil effects are illustrated for REMPI of D atoms cooled in a supersonic discharge expansion. Dramatic effects of recoil are also illustrated here for the photodissociation of HI. Recoil effects are shown to play a role in the final resolution of many types of velocity mapping experiments.