Thomas Jagau from Leuven gives a colloquium titled "Modeling Auger spectroscopy with complex scaling". Fika will be served afterwards.
The interaction of molecules with radiation can lead to the formation of metastable states, also called electronic resonances, that decay by emission of electrons. A prominent example of such nonradiative decay is the Auger process that core-ionized states undergo. While Auger electrons have kinetic energies of 100 eV or even 1000 eV, there are also electronic resonances that lead to the emission of electrons with much less energy, for example, in interatomic/intermolecular Coulombic decay, electron scattering, and photodetachment.
The theoretical modeling of Auger decay and similar processes with quantum chemistry is difficult because electronic resonances are embedded in the continuum and not L² integrable. An elegant way to address this problem is provided by non-Hermitian quantum mechanics. Techniques such as complex scaling and complex-scaled basis functions produce Hamiltonians with complex-valued energy eigenvalues whose imaginary part describes the rate of decay. This allows for the extension of bound-state quantum chemistry to electronic resonances.
In this talk, I will present the theory of complex scaling, strategies for its integration into bound-state quantum chemistry, and present some recent applications to Auger spectroscopy.