Slice imaging and velocity mapping using a single field

In this study we demonstrate that it is possible to perform velocity mapping and slice imaging of charged particle products using a single field (two electrodes) improving on the multielectrode geometries of the past. The performance of this new geometry is competitive to the multielectrode ones, presently limited by detector spot resolution. For imaging both photoelectrons and photofragments a resolution of similar to 1% in velocity is achieved without further software manipulation such as event counting. The advantages of this new design are its ability to focus large volumes, its achromaticity (very little sensitivity on photofragment velocities), independence of the laser beam position in the field perpendicular to the extraction field, and compactness. Using this new design we have studied the photodissociation dynamics of pyrrole at 243 nm and show that internal conversion of electronically excited state molecules to the ground state is important even at such low excitation energies. (c) 2006 American Institute of Physics.