Physical Review Research (Jul 2020)
Revealing the two-electron cusp in the ground states of He and H_{2} via quasifree double photoionization
Abstract
We report on kinematically complete measurements and ab initio nonperturbative calculations of double ionization of He and H_{2} by a single 800 eV circularly polarized photon. We confirm the quasifree mechanism of photoionization for H_{2} and show how it originates from the two-electron cusp in the ground state of a two-electron target. Our approach establishes a method for mapping electrons relative to each other and provides valuable insight into photoionization beyond the electric-dipole approximation.