Effect of intermediate coupling on angular distribution of Auger electrons

Auger electron angular distributions following excitation or ionization from the Xe 3d and F 1s levels in xenon difluoride

Linearly polarized synchrotron radiation has been used to record polarization dependent, non-resonant Auger electron spectra of XeF₂, encompassing the bands due to the xenon M₄₅N₁N₄₅, M₄₅N₂₃N₄₅, M₄₅N₄₅N₄₅ and M₄₅N₄₅V and fluorine KVV transitions. Resonantly excited Auger spectra have been measured at photon energies coinciding with the Xe 3d_5/2 → σ* and the overlapped Xe 3d_3/2/F 1s → σ* excitations in XeF₂. The non-resonant and resonantly excited spectra have enabled the Auger electron angular distributions, as characterized by the β_A parameter, to be determined for the M₄₅N₄₅N₄₅ transitions. In the photon energy range over which the Auger electron angular distributions were measured, theoretical results indicate that transitions into the εf continuum channel dominate the Xe 3d photoionization in XeF₂. In this limit, the theoretical value of the atomic alignment parameter (A₂₀) characterizing the core ionized state becomes constant. This theoretical value has been used to obtain the Auger electron intrinsic anisotropy parameters (α₂) from the β_A parameters extracted from our non-resonant Auger spectra. For a particular Auger transition, the electron kinetic energy measured in the resonantly excited spectrum is higher than that in the directly ionized spectrum, due to the screening provided by the electron promoted into the σ* orbital. The interpretation of the F KVV Auger band in XeF₂ has been discussed in relation to previously published one-site populations of the doubly charged ions (XeF₂²⁺). The experimental results show that the ionization energies of the doubly charged states predominantly populated in the decay of a vacancy in the F 1s orbital in XeF₂ tend to be higher than those populated in the decay of a vacancy in the Xe 4d level in XeF₂.