29 research outputs found
Development of a spectro-electrochemical cell for soft X-ray photon-in photon-out spectroscopy
We developed a spectro-electrochemical cell for X-ray absorption and X-ray emission spectroscopy, which are element-specific methods to study local electronic structures in the soft X-ray region. In the usual electrochemical measurement setup, the electrode is placed in solution, and the surface/interface region of the electrode is not normally accessible by soft X-rays that have low penetration depth in liquids. To realize soft X-ray observation of electrochemical reactions, a 15-nm-thick Pt layer was deposited on a 150-nm-thick film window with an adhesive 3-nm-thick Ti layer for use as both the working electrode and the separator window between vacuum and a sample liquid under atmospheric pressure. The designed three-electrode electrochemical cell consists of a Pt film on a SiC window, a platinized Pt wire, and a commercial Ag|AgCl electrode as the working, counter, and reference electrodes, respectively. The functionality of the cell was tested by cyclic voltammetry and X-ray absorption and emission spectroscopy. As a demonstration, the electroplating of Pb on the Pt/SiC membrane window was measured by X-ray absorption and real-time monitoring of fluorescence intensity at the O 1s excitation
Interpretation of the X-Ray Emission Spectra of Liquid Water through Temperature and Isotope Dependence
The interpretation of x-ray emission spectroscopy (XES) spectra in terms of their sensitivity to the hydrogen bonding and the consequent microheterogeneity in liquid water has been debated over a decade. To shed a light on this problem, we report the theoretical reproduction of the debated 1b_{1} peaks observed in the XES spectra of liquid water using semiclassical Kramers-Heisenberg formula. The essence of the temperature and isotope dependence of the 1b_{1} double peaks is explained by molecular dynamics simulations including full vibrational (O─H stretching, bending, and) modes, rotational combined with the density functional theory and core-hole induced dynamics. Some inconsistencies exist with the experimental XES profile, which illustrates the need to employ a more precise theoretical calculations for both geometry sampling and electronic structure using a more sophisticated procedure
Correlation between soft X‑ray absorption and emission spectra of the nitrogen atoms within imidazolium-based ionic liquids
Soft
X-ray absorption spectroscopy (XAS) has been performed on
the N K-edge of two imidazolium-based ionic liquids (ILs), 1-ethyl-3-methylimidazolium
bis(trifluoromethylsulfonyl)amide ([C<sub>2</sub>mim][TFSA]) and 1-ethyl-3-methylimidazolium
bromide ([C<sub>2</sub>mim][Br]), to clarify the electronic structures
of the ILs. Soft X-ray emission spectroscopy (XES) has also been applied
to the ILs by excitation at various X-ray energies according to the
XAS spectra. It was possible to fully associate
the XAS peaks with the XES peaks. Additionally, both XAS and XES spectra
of the ILs were well reproduced by the theoretical spectra for a single-molecule
model on [C<sub>2</sub>mim]<sup>+</sup> and [TFSA]<sup>−</sup> using density functional theory. The assignments for the XAS and
XES peaks of the ILs were accomplished from both experimental and
theoretical approaches. The theoretical XAS and XES spectra of [C<sub>2</sub>mim]<sup>+</sup> and [TFSA]<sup>−</sup> did not significantly
depend on the conformations of the ions. The reproducibility of the
theoretical spectra for the single-molecule model suggested that the
interactions between the cations and anions are very weak in the ILs,
thus scarcely influencing the electronic structures of the nitrogen
atoms