Figure 2: Electronic level scheme and emission spectrum.
From: Sensitivity of nonlinear photoionization to resonance substructure in collective excitation
Electron spectrum from XUV-ionized xenon atoms, recorded at hν=105 eV with a FEL irradiance of (6±2) × 1012 W cm−2, is shown along with the energy level scheme for the xenon orbitals involved in the ionization processes. The spectrum includes features coming from electron emission caused by different processes represented by arrows: 1-photon direct emission (black), Auger emission (green) and 2-photon direct emission (red). In the low-KE region (KE <50 eV) the spectrum is dominated by the contribution from the 4d (1-photon) photoemission and by the subsequent Auger decays involving the 5s and the 5p shells. The small features at KE between 80 and 100 eV arise from the 1-photon photoemission from 5s and 5p shells. The high-energy feature is assigned to the 2-photon photoemission from the 4d shell.
