Electronic Polarization Effects in Core-Level Spectroscopy

TL;DR

This paper investigates how electronic polarization affects core-level energies in X-ray photoelectron spectroscopy, demonstrating significant shifts and providing an analytical model that aligns well with experimental data.

Contribution

It introduces an analytical formula based on classical electrostatics to accurately describe polarization effects in noble gas clusters, improving understanding and computational efficiency.

Findings

Polarization shifts core-level energies by over 1 eV.

The polarization energy is similar across different core orbitals of an atom.

The analytical model agrees well with experimental data.

Abstract

In X-ray photoelectron spectroscopy (XPS), the injected hole interacts with the electronic polarization cloud induced by the hole itself, ultimately resulting in a lower binding energy. Such polarization effect can shift the core-level energy by more than 1 eV, as shown here by embedded many-body perturbation theory for the paradigmatic case of noble gas clusters made of Ar, Kr, or Xe. The polarization energy is almost identical for the different core-orbitals of a given atom, but it strongly depends on the position of the ionized atom in the cluster. An analytical formula is derived from classical continuum electrostatics, providing an effective and accurate description of polarization effects, which permits to achieve an excellent agreement with available experiments on noble gas clusters at a modest computational cost. Electronic polarization provides a crucial contribution to core levels absolute energies and chemical shifts.