| 1. |
- Chuang, Yi-De, et al.
(författare)
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Modular soft x-ray spectrometer for applications in energy sciences and quantum materials
- 2017
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 88:1
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Tidskriftsartikel (refereegranskat)abstract
- Over the past decade, the advances in grating-based soft X-ray spectrometers have revolutionizedthe soft X-ray spectroscopies in materials research. However, these novel spectrometers are mostlydedicated designs, which cannot be easily adopted for applications with diverging demands. Here wepresent a versatile spectrometer design concept based on the Hettrick-Underwood optical scheme thatuses modular mechanical components. The spectrometer’s optics chamber can be used with gratingsoperated in either inside or outside orders, and the detector assembly can be reconfigured accordingly.The spectrometer can be designed to have high spectral resolution, exceeding 10 000 resolvingpower when using small source (∼1 µm) and detector pixels (∼5 µm) with high line density gratings(∼3000 lines/mm), or high throughput at moderate resolution. We report two such spectrometers withslightly different design goals and optical parameters in this paper. We show that the spectrometer withhigh throughput and large energy window is particularly useful for studying the sustainable energymaterials. We demonstrate that the extensive resonant inelastic X-ray scattering (RIXS) map of batterycathode material LiNi1/3Co1/3Mn1/3O2 can be produced in few hours using such a spectrometer.Unlike analyzing only a handful of RIXS spectra taken at selected excitation photon energies across theelemental absorption edges to determine various spectral features like the localized dd excitations andnon-resonant fluorescence emissions, these features can be easily identified in the RIXS maps. Studyingsuch RIXS maps could reveal novel transition metal redox in battery compounds that are sometimeshard to be unambiguously identified in X-ray absorption and emission spectra. We propose that thismodular spectrometer design can serve as the platform for further customization to meet specificscientific demands.
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| 2. |
- Shao, Yu-Cheng, et al.
(författare)
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The key energy scales of Gd-based metallofullerene determined by resonant inelastic X-ray scattering spectroscopy
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Endohedral metallofullerenes, formed by encaging Gd inside fullerenes like C80, can exhibit enhanced proton relaxitivities compared with other Gd-chelates, making them the promising contrast agents for magnetic resonance imaging (MRI). However, the underlying key energy scales of Gd x Sc3-x N@C80 (x = 1-3) remain unclear. Here, we carry out resonant inelastic X-ray scattering (RIXS) experiments on Gd x Sc3-x N@C80 at Gd N 4,5-edges to directly study the electronic structure and spin flip excitations of Gd 4f electrons. Compared with reference Gd2O3 and contrast agent Gadodiamide, the features in the RIXS spectra of all metallofullerenes exhibit broader spectral lineshape and noticeable energy shift. Using atomic multiplet calculations, we have estimated the key energy scales such as the inter-site spin exchange field, intra-atomic 4f-4f Coulomb interactions, and spin-orbit coupling. The implications of these parameters to the 4f states of encapsulated Gd atoms are discussed.
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| 3. |
- Tu, Chien Ming, et al.
(författare)
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Helicity-dependent terahertz emission spectroscopy of topological insulator S b2 T e3 thin films
- 2017
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Ingår i: Physical Review B. - 2469-9950. ; 96:19
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Tidskriftsartikel (refereegranskat)abstract
- We report on helicity-dependent terahertz emissions that originate from the helicity-dependent photocurrents in topological insulator Sb2Te3 thin films due to ultrafast optical excitation. The polarity of the emitted terahertz radiation is controlled by both the incident angle and the helicity of optical pulses. Using an unprecedented decomposition-recombination procedure in the time domain, the signals of the Dirac fermions are fully separated from bulk contributions. These results provide insights into the optical coupling of topological surface states and open up opportunities for applying helicity-dependent terahertz emission spectroscopy in spintronics.
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