  Electronic decay processes like the Auger-Meitner process and the
Interparticle Coulombic Decay (ICD) are omnipresent and occur in areas like
metallurgy, analysis of surfaces, semi-conductors, water, solvents, noble gas
clusters and even in the active centers of proteins. These processes are
initated by removal or excitation of a sub-outervalence electron, which can be
achieved by, e.g., light in the XUV to x-ray range. These energies allow the
creation of ultrashort laser pulses and hence time-resolved measurements with
high time resolutions.
  So far, electronic decay processes were described by Fano's theory. However,
this theory considers only the involved electronic states while neglecting the
nuclear parts of the wavefunction. Especially in the case of ICD, though, the
nuclear dynamics are required for an accurate description. We therefore present
an analytical ansatz for the explicit inclusion of the nuclear wavefunction
within the Born-Oppenheimer approximation into Fano theory.
  We thereby gain a model, which can serve for illustrative interpretations of
electronic decay processes, in which nuclear motion is relevant.
