Spatial and Momentum Mapping Modes for Velocity Map Imaging Spectrometer

Abstract

The velocity map imaging (VMI) technique is used to acquire the momentum distribution of charged particles. Here, we introduce two additional operation modes for our recently built velocity map imaging (VMI) spectrometer: the spatial mapping mode that magnifies the image of zero energy ions with different scales and the high-resolution momentum mapping mode that acquires the electron momentum distribution at the kinetic energy of about 100 eV. In simulations, the ion image is magnified with a factor of up to 7.6, and a relative resolution of 0.15% at 150 eV electron kinetic energy is predicted. Switching between these two modes helps reduce the alignment error to below 0.2 mm. In the test using the above-threshold ionization (ATI) of argon (Ar), the Ar+ ion image is magnified by a factor of up to 6.7, and a relative resolution of 1.3% at 44.6 eV electron kinetic energy is achieved.