Abstract
In this work, we outline a general method for calculating Auger spectra in molecules, which accounts for the underlying symmetry of the system. This theory starts from Fano’s formulation of the interaction between discrete and continuum states, and it generalizes this formalism to deal with the simultaneous presence of several intermediate quasi-bound states and several non-interacting decay channels. Our theoretical description is specifically tailored to resonant autoionization and Auger processes, and it explicitly includes the incoming wave boundary conditions for the continuum states and an accurate treatment of the Coulomb repulsion. This approach is implemented and applied to the calculation of the K−LL Auger and autoionization spectra of ozone, which is a C2v symmetric molecule, whose importance in our atmosphere to filter out radiation has been widely confirmed. We also show the effect that the molecular point group and, in particular, the localization of the core-hole in the oxygen atoms related by symmetry operations, has on the electronic structure of the Auger states and on the spectral lineshape by comparing our results with the experimental data.
Highlights
We show the effect that the molecular point group and, in particular, the localization of the core-hole in the oxygen atoms related by symmetry operations, has on the electronic structure of the
The ozone ground state has a trigonal planar bent molecular geometry belonging to the C2v symmetry group, whereby the central oxygen atom is in a sp2 -hybridized configuration
The ozone geometry was relaxed below 10−3 Ry/Å for the interatomic forces via first-principles density functional theory (DFT) calculations, as implemented in the Quantum Espresso code suite [22], using a PBE-GGA functional [23]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Afterwards, the excited system undergoes a dissociative path into final channels that are characterized by the presence of a few asymptotically non-interacting fragments, the observation of which provides useful information on the properties of the system under examination These decay processes are due to the fact that the resonant excited state that is produced by the initial collision with the high-energy photon is embedded in the continua of the final fragments. From the standpoint of computation, one notes the existence of an ample body of techniques developed for atomic systems, whereas, for molecules, the number is much more limited [13,14] This is mainly due to the difficulties that are created by the reduced symmetry of molecular systems, which hinders the use of numerical techniques for representing the electron as it moves outward through the field of the ionized molecule. The effect on the Auger lineshape of the presence of core-hole localized in the 1s orbitals of symmetry-related oxygen atoms, rather than in a delocalized molecular orbital, is discussed
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