Quantitative analysis by X-ray induced total electron yield (TEY) compared to XRFA

Ebel, H.

doi:10.1154/1.1649329

Cited by 4 publications

(2 citation statements)

References 31 publications

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“…The overall angular dependence of the TEY signal is sufficiently involved to merit a separate consideration. [88][89][90] To circumvent these difficulties in the next section we use instead x-ray reflectometry, which in addition to chemical and valence profiles allows for extraction of atomic scattering factors in absolute units.…”

Section: 𝑀45-edge Fit To Crystal Field Calculationsmentioning

confidence: 99%

Chemical and valence reconstruction at the surface ofSmB6revealed by means of resonant soft x-ray reflectometry

et al. 2018

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Samarium hexaboride (SmB6), a Kondo insulator with mixed valence, has recently attracted much attention as a possible host for correlated topological surface states. Here, we use a combination of x-ray absorption and reflectometry techniques, backed up with a theoretical model for the resonant 4,5 absorption edge of Sm and photoemission data, to establish laterally averaged chemical and valence depth profiles at the surface of SmB6. We show that upon cleaving, the highly polar (001) surface of SmB6 undergoes substantial chemical and valence reconstruction, resulting in boron termination and a Sm 3+ dominated sub-surface region. Whereas at room temperature, the reconstruction occurs on a time scale of less than two hours, it takes about 24 hours below 50 K. The boron termination is eventually established, irrespective of the initial termination. Our findings reconcile earlier depth resolved photoemission and scanning tunneling spectroscopy studies performed at different temperatures and are important for better control of polarity and, as a consequence, surface states in this system.

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Section: 𝑀45-edge Fit To Crystal Field Calculationsmentioning

confidence: 99%

Chemical and valence reconstruction at the surface ofSmB6revealed by means of resonant soft x-ray reflectometry

et al. 2018

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“…The magnitude of this current can serve as a measure of the incident or absorbed photon flux. This measurement mode is often referred to as total electron yield since all electrons that emerge from the surface as a result of photoemission are detected, independent of their energy (e.g., [8][9][10]).…”

Section: Introductionmentioning

confidence: 99%

Flux monitoring hard X-ray optics in a single electrode configuration

Stoupin,

Shi,

Katsoudas

2014

Preprint

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To explore possibilities for X-ray flux monitoring on optical elements electrical responses of silicon and diamond single crystals and that of an X-ray mirror were studied under exposure to hard X-rays in a single electrode configuration in ambient air. To introduce flux monitoring as a non-invasive capability a platinum electrode was deposited on a small unexposed portion of the entrance surface of the crystals while for the X-ray mirror the entire mirror surface served as an electrode. It was found that the electrical responses are affected by photoemission and photoionization of the surrounding air. The influence of these factors was quantified using estimations of total electron yield and the ionization current. It is shown that both phenomena can be used for the non-invasive monitoring of hard X-ray flux on the optical elements. Relevant limits of applicability such as detection sensitivity and charge collection efficiency are identified and discussed.

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An XAS study of the sulfur environment in human neuromelanin and its synthetic analogs

et al. 2009

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Neuromelanin is a complex molecule accumulating in the catecholaminergic neurons that undergo a degenerative process in Parkinson's disease. It has been shown to play either a protective or a toxic role depending on whether it is present in the intraneuronal or extraneuronal milieu. Understanding its structure and synthesis mechanisms is mandatory to clarify the reason for this remarkable dual behavior. In the present study, X-ray absorption spectroscopy is employed to investigate the sulfur binding mode in natural human neuromelanin, synthetic neuromelanins, and in certain structurally known model compounds, namely cysteine and decarboxytrichochrome C. Based on comparative fits of human and synthetic neuromelanin spectra in terms of those of model compounds, the occurrence of both cysteine- and trichochrome-like sulfur coordination modes is recognized, and the relative abundance of these two types of structural arrangement is determined. Data on the amount of cysteine- and trichochrome-like sulfur measured in this way indicate that among the synthetic neuromelanins those produced by enzymatic oxidation are the most similar ones to natural neuromelanin. The interest of the method described here lies in the fact that it allows the identification of different sulfur coordination environments in a physically nondestructive way.

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Quantitative analysis by X-ray induced total electron yield (TEY) compared to XRFA

Cited by 4 publications

References 31 publications

Chemical and valence reconstruction at the surface ofSmB6revealed by means of resonant soft x-ray reflectometry

Chemical and valence reconstruction at the surface ofSmB6revealed by means of resonant soft x-ray reflectometry

Flux monitoring hard X-ray optics in a single electrode configuration

An XAS study of the sulfur environment in human neuromelanin and its synthetic analogs

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