Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.

Chemical effect on the K and L shell intensity ratios of Hf compounds

Abstract: Chemical effects on the Ki/Kj (i=α2, β, β1, β2; j=α, α1, β1), Li/Lα (i=l, β, γ) and Li/Kj (i=l,α, β, γ; j=α1, α2) x-ray intensity ratios for (Hf) compounds were investigated. The samples were excited by 123.6 keV γ-rays from a 57Co annular radioactive source. K and L x-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. We observed a chemical effect on the Li/La and Li/Kj x-ray intensity ratios for Hf compounds. However, for the Ki/Kj intensity ratios, dependence on the chemical state of Hf compounds is almost negligible. The experimental values have been compared with the theoretically calculated values of pure Hf.

X-ray spectroscopic application of Cr∕Sc periodic multilayers

Abstract: The use of Cr∕Sc multilayer interferential mirrors (MIMs) in optical systems such as x-ray microscopes or telescopes have been reported for the water window (between C K- and O K-absorption edges). However, their possibilities in spectroscopic application have never been described in the literature. The purpose of the paper is to report for the first time on the performances of Cr∕Sc MIMs as Bragg dispersive devices for the analysis in wavelength dispersive spectrometry of samples containing N or Sc atoms. The possibility to distinguish the chemical state of the emitting N or Sc atoms is evidenced by using Johan-type and double-crystal spectrometers.

Photoreactivity of Si(111)−H in Ambient

Abstract: Second harmonic generation rotational anisotropy (SHG-RA) provides a convenient means to monitor the chemical state of the Si surfaces and to follow the conversion of a H-terminated surface to SiO2 by oxidation as a function of time in ambient. SHG at 800 nm is sensitive to changes in the surface electronic properties induced by oxidation, and it probes both the initial stage of oxidation and the logarithmic oxide growth. We found that intense, ultrashort (4 ps) 800 nm laser pulses accelerate the initial stage of oxidation of Si(111)−H in ambient. The cross-section of the photoinduced process was found to be (1.7 ± 0.5) × 10-23 cm2. A mechanism involving drift of photoexcited electrons toward the surface is proposed to explain the photooxidation.

Effects of Ce, Mo and Si ion implantation on the passive layer composition and high‐temperature oxidation behaviour of AISI 304 stainless‐steel studied by soft x‐ray absorption spectroscopy

Abstract: The influence of Ce, Mo and Si ion implantation on the chemical properties of AISI 304 stainless-steel passive and oxide layers was studied by means of soft x-ray absorption spectroscopy (XAS). Applying this technique at the transition metal 2p absorption thresholds, the composition and chemical state of the passive layer were determined. A surface Cr enrichment is observed for the ion-implanted samples in comparison with non-implanted samples, which can be associated with better corrosion behaviour. To investigate the effects of ion implantation on the high-temperature oxidation behaviour of AISI 304 stainless-steel, the oxide layer formed after an isothermal oxidation at 1173 K for 32 h was also investigated. The XAS data show mainly the presence of Cr and Mn oxides in the surface region of all samples. The Cr/Fe ratio-a parameter that can be associated with the protective character of the oxide scale-is higher for the Si- and Ce-implanted samples than for the as-received sample. The Mo-implanted sample has the lowest Cr/Fe ratio, suggesting a poor oxidation resistance at high temperatures in this case.