Carbon K-edge x-ray emission spectroscopy of gas phase ethylenic molecules

Abstract

We report on the C K-edge x-ray absorption spectra and the resonant (RXES) and non-resonant (NXES) x-ray emission spectra of ethylene, allene and butadiene in the gas phase. The RXES and NXES show clear differences for the different molecules. Overall both types of spectra are more structured for ethylene and allene, than for butadiene. Using density functional theory–restricted open shell configuration interaction single calculations, we simulate the spectra with remarkable agreement with the experiment. We identify the spectral features as being due to transitions involving localised 1s orbitals. For allene, there are distinct spectral bands that reflect transitions predominantly from either the central or terminal carbon atoms. These results are discussed in the context of ultrafast x-ray studies aimed at detecting the passage through conical intersections in polyatomic molecules.

Jahn–Teller effects in initial and final states: high-resolution X-ray absorption, photoelectron and Auger spectroscopy of allene

“…Previous electron energy loss measurements 101 had attributed the feature to a combination of two overlapping 1sp* transitions, though from the limitations of the resolution of the electron energy loss spectra and available XPS measurements it was unclear as to whether the energetic separation of the transitions arose from a difference in the energy of the initial core-hole states (0.3 eV based on the XPS measurements) on the central and terminal carbons or the final p* states, as both are expected to be degenerate. 102 The theoretical spectra modelled for the minimum energy structure are presented in Fig. S11 in ESI † at the CVS-EOM-EE-CCSD and TDDFT levels.…”

Simulating fluorine K-edge resonant inelastic X-ray scattering of sulfur hexafluoride and the effect of dissociative dynamics

“…The DFT-ROCIS protocol [31] was developed in ORCA [30] to simulate K-and L-edge XA and RIXS spectra of transition metal complexes, which are particularly challenging and require efficient algorithms. However, with it has been shown to accurately predict the XA and RIXS spectra of main group element compounds [42], and thus can be for the fluorine K-edge spectra of SF 6 . For RIXS simulations, the DFT-ROCIS method requires defining three manifolds of orbitals, which are derived from the ground state wave function.…”

“…Here in this work, we simulated a static XE spectrum of SF 6 with a protocol based on DFT-ROCIS RIXS module in ORCA, previously applied to a series of alkenes [42]. The details of this protocol have already been discussed in detail in the Methods section II and in Ingle et al [42]. In comparison to the Kohn-Sham orbital approximation presented in Fig.…”

“…4, we simulated the static F1s RIXS spectra of SF 6 in the same theoretical framework using DFT-ROCIS and TD-DFT. The TD-DFT protocol within the restricted subspace approximation [50] and DFT-ROCIS/B3LYP were chosen as methods of choice since they have been shown to perform well in simulating RIXS spectra in number of earlier studies [42,60]. The computational details are given in the Methods section II.…”

Mapping the electronic transitions of protonation sites in peptides using soft X-ray action spectroscopy

“…53,54 Such a method has already been used successfully to compare DFT calculations with soft X-ray absorption spectra. 15,17,23,55…”