Iron L-Edge Absorption Spectroscopy of Iron Pentacarbonyl and Ferrocene in the Gas Phase

Abstract

Fe L-edge X-ray absorption spectra of gas-phase iron pentacarbonyl and ferrocene measured in total-ion yield mode are reported. Comparison to previously published spectra of free iron atoms and gaseous iron chloride demonstrates how the interplay of local atomic multiplet effects and orbital interactions in the metal-ligand bonds varies for the different systems. We find changes in the degree of metal-ligand covalency to be reflected in the measured 2p absorption onset. Orbital- or state-specific fragmentation is furthermore investigated in iron pentacarbonyl and ferrocene by analyzing the partial-ion-yield spectra at the Fe L-edge. Strong dependence of the yields of different fragments is observed in ferrocene in contrast to iron pentacarbonyl. This difference is attributed to the different degrees to which the 2p core hole is screened in the two systems and to which charge is rearranged in the Auger final states. We provide experimental benchmark spectra for new ab initio approaches for calculating metal L-edge absorption spectra of metal complexes.

Covalency‐Driven Preservation of Local Charge Densities in a Metal‐to‐Ligand Charge‐Transfer Excited Iron Photosensitizer

“…We establish this general mechanism by studying the valence electronic structure of the 3 MLCT state of the complex [Fe(bpy)(CN) 4 ] 2À using time-resolved Xray absorption spectroscopy (XAS) at the Fe L-edge.T he underlying 2p!3d excitation locally probes the density of unoccupied states around the metal center and is thereby sensitive to metal-ligand covalency, [17][18][19] the metal oxidation state [13,20] and local charge distribution. [21,22] Applied within an optical-pump X-ray-probe scheme,t he method extends its sensitivity to valence-excited states by directly monitoring optically induced changes in the occupation of 3d-derived orbitals. [23] By combining time-resolved L-edge XAS with density functional theory (DFT) we can therefore provide adetailed analysis of the 3 MLCT valence electronic structure and relate the photo-induced spectral changes to variations in local charge and spin densities.…”

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

“…However, this effect has to be studied in more detail. Transition metal L-edge spectra exhibit usually very sharp and intense LUMO peaks excelling non-resonant absorption cross-section by several factors [46,102,103]. The X-ray absorption resonances of the applied precursor molecules should, therefore, be much more dominant compared to the present results of growth rate enhancements of up to 40% [21,22].…”

“…A potential strength, however, may be photon energy dependent fragmentation of precursor molecules, which has potential to further enhance the in-situ purity of the resulting FXBID deposits. It has been shown that X-ray induced fragmentation of certain relevant precursor molecules exhibits photon energy dependency not only in terms of fragmentation rates, but also fragmentation chemistry, i.e., changing relative intensities of various fragments [103,118,119]. Such effects could be exploited to select photon energies for FXBID that result in a high ratio of low mass fragments (in ideal cases only the metal center itself) versus high mass fragments leading to implantation of a large amount of alien atoms from the ligands into the resulting deposits.…”

Improved charge transfer multiplet method to simulateM- andL-edge X-ray absorption spectra of metal-centered excited states

“…The following references are cited in the supporting information for this article: Berlasso et al (2006); Godehusen et al (2017); Ryland et al (2018).…”