Effects of molecular potential and geometry on atomic core-level photoemission over an extended energy range - the case study of CO molecule

E Kukk,M Kimura,P Decleva,L Argenti,K Ueda,M Patanen,S Mondal,T D Thomas,A Palacios,C Miron,K Sakai,E Plésiat,D Ayuso,O Travnikova,F Martín,K Kooser

doi:10.1088/1742-6596/488/2/022040

Abstract

We report an experimental and theoretical study of single-molecule inner-shell photoemission over an extended range of photon energies. The vibrational ratios v=1/v=0 from the C 1s photoelectron spectra, although mostly determined by the bond length change, are shown to be affected also by photoelectron recoil and scattering on the neighboring oxygen atom. Density functional theory is used to encompass all these effect in unified treatment. It is also demonstrated that the DFT calculations can be used as a means to extract dynamic and static molecular geometry values.

Highlights

Diatomic molecules in the gas phase have long been of fundamental scientific interest as the simplest quantum mechanical systems combining fast and slow dynamics
We show in a systematic approach how the bond contraction, intramolecular scattering (R0-dependent effect), and recoil excitations together determine the v-ratios observed in the C 1s photoelectron spectra
The theoretical results included conventional Franck-Condon excitations, photoelectron recoil, and intramolecular scattering on the neighboring oxygen atom

Summary

INTRODUCTION

Diatomic molecules in the gas phase have long been of fundamental scientific interest as the simplest quantum mechanical systems combining fast (electronic) and slow (nuclear) dynamics. Core-level photoelectron spectroscopy was found to be an excellent means to elicit information on molecular dynamics: the disturbance to the electronic structure by core hole creation induces changes in equilibrium structural parameters, causing readjustment of atomic positions and resulting in vibrational excitations [6]. We have employed static-exchange density functional theory to obtain ab initio vibrationally resolved cross-sections of the C 1s photoemission for ν = 0 and ν = 1 levels. These molecular effects are superimposed on the atomic cross section, which falls off sharply with increasing photon energy. We show in a systematic approach how the bond contraction, intramolecular scattering (R0-dependent effect), and recoil excitations together determine the v-ratios observed in the C 1s photoelectron spectra. This work is a proof of principle that such a theoretical approach can be used to determine both the static and dynamic structural properties of a molecule at the same time

EXPERIMENTS AND DATA TREATMENT

THEORY

Static-exchange DFT results

Comparison with experiment and derivation of geometrical parameters

CONCLUSION