Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100 eV: probing first-row transition-metalM-edges in chemical complexes

Abstract

X-ray absorption and scattering spectroscopies involving the 3d transition-metal K-and L-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M-edges, which are below 100 eV. Synchrotron-based X-ray sources can have higher energy resolution at M-edges. M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information to K-and L-edge spectroscopies. In this study, M 2,3 -edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M 2,3 -edge RIXS on NiO, NiF 2 and two other covalent complexes have been performed and different d-d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M-edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100 eV is also illustrated and discussed.

Sub-100 fs Intersystem Crossing to a Metal-Centered Triplet in Ni(II)OEP Observed with M-Edge XANES

“…Ab initio semiempirical multiplet calculations were performed using a version of the charge-transfer multiplet code CTM4XAS; this model has been used extensively for simulating L 2,3 -edge XAS − and more recently for simulating M 2,3 -edge XAS − of transition-metal complexes. Briefly, the metal center is modeled using a parametric Hamiltonian containing electron–nuclear and electron–electron Coulombic interactions, spin-orbit coupling, and an electrostatic crystal field. , Metal–ligand hybridization is included as a configuration interaction term between 3d 8 and 3d 9 L configurations, where L designates a hole on the ligand.…”

Nickel Oxidation States and Spin States of Bioinorganic Complexes from Nickel L-edge X-ray Absorption and Resonant Inelastic X-ray Scattering

“…For NiO excited at 852.7 eV (a), the main L 3 RIXS peak is at 851.0 eV, which is 1.7 eV lower than the excitation energy. It is known that NiO has three d−d transitions at about 1.0, 1.8 (or 1.6), and 3.0 eV from previous K-, 32 L-, 33 and M- 31,34 edge Ni RIXS. The 851.0 eV RIXS profile (in Figure 3) is centered at about −1.7 eV and covers all three d−d peaks, although the lowest and highest peaks are weaker and unresolved.…”

Shrinking the Synchrotron: Tabletop Extreme Ultraviolet Absorption of Transition-Metal Complexes

“…Simulated spectra are computed using the ligand-field multiplet (LFM) model that takes into account angular momentum coupling between 3d electrons and the 2p/3p core hole. This model has been widely used to treat L 2,3 edge spectra, and has been applied to a handful of M 2,3 -edge spectra of inorganic complexes. − The crystal field splitting parameter 10Dq for each complex was taken from UV/visible data or L 2,3 -edge studies. Calculated spectra are broadened with a Gaussian function to account for the spectrometer resolution (σ = 0.2 eV), with a Fano line shape to account for interference between direct 3d photoionization and 3p3d3d Auger emission ( q = 3.5) and with a Lorentzian function to account for the intrinsic lifetime of each final state.…”

“…The sensitivity of M-edge spectroscopy to the electronic structure of first-row transition-metal complexes was predicted as early as 1991 and observed in transition-metal oxides − , and halides , but until now has not been demonstrated in molecular systems. There are two fundamental challenges to absorption spectroscopy at the M edge, as compared to the L and K edges.…”