Coulomb Explosion Imaging: Super-Resolution by Optical Properties of Electrostatics Lenses

Velocity-map imaging (VMI) is a popular technique in a Coulomb-explosion imaging experiment with the capacity to focus photo-fragments based on their initial velocity vectors. The VMI is capable of achieving this feat as a result of the system of electrostatic lenses with varying potential, which the photo-fragments have to transit. However, despite the focusing capability of the VMI, the measured time-of-flights of the photo-fragments still suffer from a temporal spread, which is a consequence of the initial velocity and spatial spread at the point of formation. To be able to improve the spatial-temporal resolution of the photo-fragments at the point of formation, there is a need for a better understanding of how the system of electrostatic lenses alter the trajectories of the photo-fragments between formation and detection to achieve a velocity map. Also, an expression is derived to resolve the spatial spread of the photo-fragment products.