Recovery of kinetic energies and angular distributions of photoelectrons by spatial map imaging

  Rami Rahimi  ,  Yair Yifrach  ,  Alexander Portnov   ,  Ilana Bar  
Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel

Particle imaging can be accomplished by electrostatic lenses, through velocity map imaging (VMI) and spatial map imaging (SMI). Here an approach was devised to calculate the SMI patterns mapping the position coordinates and velocity vector, while considering the angular distributions of charged particles on the detector. This was achieved by analyzing and modelling the simulated patterns, convoluting them with a line, to form horizontal stripes, SMIs, depending on the initial velocities and the angular distributions. A proof-of-concept study, using resonant ionization in a standard three-electrode electrostatic lens system, operated at low acceleration voltages, was performed on water in a selected rotational state, leading to a measured SMI pattern of the ejected photoelectrons (PE). The resulting unique intensity profiles, along the central vertical line, were least-square fitted with the values resulting from computed data sets, accounting for various kinetic energies (KE) and anisotropy parameters, . The best-fitted values provided the KE release and  for the ejected PEs, allowing to reveal their binding energy and angular distribution. It is expected that this new approach will be applicable to a wide range of processes and valuable for determining the above parameters for signals of particles suffering from high background levels.