Core-hole localization and ultra-fast dissociation in SF6

V Ekholm,M Odelius,F Gel’Mukhanov,M Simon,M Guarise,C Såthe,G S Chiuzbǎian,O Björneholm,A Nicolaou,C F Hague,N Jaouen,J Lüning,J-E Rubensson

doi:10.1088/1361-6455/aba204

Abstract

Resonant inelastic x-ray scattering spectra excited at the fluorine K resonances of SF6 have been recorded. While a small but significant propensity for electronically parity-allowed transitions is found, the observation of parity-forbidden electronic transitions is attributed to vibronic coupling that breaks the global inversion symmetry of the electronic wavefunction and localizes the core hole. The dependence of the scattering cross section on the polarization of the incident radiation and the scattering angle is interpreted in terms of local π/σ symmetry around the S–F bond. This symmetry selectivity prevails during the dissociation that occurs during the scattering process.

Highlights

Electronic states in a inversion-symmetric system have well-defined parity
The polarization dependence indicates that local π/σ symmetry is retained, and our analysis shows that the sharp peak primarily is associated with emission at large interatomic distances during dissociation
As emission associated with electron transfer from all valence orbitals to the core levels is allowed, and as there is no significant symmetry selectivity for excitation high above the ionization limit the discussion of local versus global symmetry selectivity becomes irrelevant for the high-energy excited spectrum

Summary

Introduction

Electronic states in a inversion-symmetric system have well-defined parity. a fluorine 1s core hole in the SF6 molecule is typically described in terms of a multiconfigurational symmetry-adapted wavefunction, comprising core holes at various fluorine sites. In resonant inelastic x-ray scattering (RIXS) symmetry breaking due to ultrafast electronic–vibronic coupling is manifested in population of electronically parity forbidden final states [3,4,5]. Even in such cases, RIXS spectra are sensitive to the symmetry of the wavefunction. Electronically dipole forbidden transitions are observed, demonstrating dynamic breaking of the global electronic inversion symmetry and suggesting core-hole localization. Analysis of the electron emission has earlier demonstrated that dissociation can occur prior to the core hole decay [14,15,16,17], and a sharp peak suggesting atomic transitions is observed in the present RIXS spectra. The polarization dependence indicates that local π/σ symmetry is retained, and our analysis shows that the sharp peak primarily is associated with emission at large interatomic distances during dissociation

Experimental

Theory

Results and discussion

Conclusion