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Stochastic stimulated electronic x-ray Raman spectroscopy
摘要： Resonant inelastic x-ray scattering (RIXS) is a well-established tool for studying electronic, nuclear, and collective dynamics of excited atoms, molecules, and solids. An extension of this powerful method to a time-resolved probe technique at x-ray free electron lasers (XFELs) to ultimately unravel ultrafast chemical and structural changes on a femtosecond time scale is often challenging, due to the small signal rate in conventional implementations at XFELs that rely on the usage of a monochromator setup to select a small frequency band of the broadband, spectrally incoherent XFEL radiation. Here, we suggest an alternative approach, based on stochastic spectroscopy, which uses the full bandwidth of the incoming XFEL pulses. Our proposed method is relying on stimulated resonant inelastic x-ray scattering, where in addition to a pump pulse that resonantly excites the system a probe pulse on a specific electronic inelastic transition is provided, which serves as a seed in the stimulated scattering process. The limited spectral coherence of the XFEL radiation defines the energy resolution in this process and stimulated RIXS spectra of high resolution can be obtained by covariance analysis of the transmitted spectra. We present a detailed feasibility study and predict signal strengths for realistic XFEL parameters for the CO molecule resonantly pumped at the O1s ! p(cid:2) transition. Our theoretical model describes the evolution of the spectral and temporal characteristics of the transmitted x-ray radiation, by solving the equation of motion for the electronic and vibrational degrees of freedom of the system self consistently with the propagation by Maxwell equations.
关键词： CO molecule,covariance analysis,Stochastic stimulated electronic x-ray Raman spectroscopy,resonant inelastic x-ray scattering,XFEL
更新于2025-09-04 15:30:14
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Note: Plasma optical emission spectroscopy for water vapor quantification and detection during vacuum drying process
摘要： A methodology involving plasma optical emission spectroscopy driven by a direct current (dc) plasma source is developed to quantify water vapor concentration in a gaseous stream. The experimental setup consists of a dc driven low-pressure plasma cell in which the emission from the plasma discharge is measured by using an optical emission spectrometer. The emission from Hα at 656.2 nm—the first transition in the Balmer series, was found to be the most sensitive to the water vapor concentration in the gas stream. Consistent linear trends of the emission signals with respect to variation in concentration of water are observed for multiple combinations of operating parameters. This method has been applied to a vacuum drying process of a mock nuclear fuel assembly to quantify the concentration of water vapor during the drying process.
关键词： Hα emission,direct current plasma source,plasma optical emission spectroscopy,vacuum drying process,water vapor quantification
更新于2025-09-04 15:30:14
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High-density cascade arc plasma sources for application to plasma windows for virtual vacuum interfaces
摘要： We develop two cascade arc plasma sources for application to plasma windows for virtual vacuum interfaces. For windowless vacuum–atmosphere separation, a compact arc discharge source having a channel diameter of 3 mm is fabricated, and an atmospheric Ar thermal plasma is generated. For an alternative differential pumping system, separating low- and high-pressure vacuum chambers, a larger arc device with an 8-mm diameter is also constructed, producing a high-density He plasma. The performances of the two cascade arcs as plasma windows are investigated. The 3-mm arc discharge generates a steep pressure gradient of Ar 100 kPa–100 Pa through the discharge channel, while the 8-mm discharge apparatus isolates the high-pressure side at 7 kPa from the lower pressure of 54 Pa. Emission spectroscopy of visible and vacuum UV radiation reveals the characteristics of the Ar and He plasmas. Spectral analysis yields a plasma temperature of around 1 eV in both discharges. Stark broadenings of the H-b and Ar I lines give an electron density of 6.5 (cid:2) 1016 cm(cid:3)3 for Ar 60 A with a gas ?ow rate of 1.0 l/min and 4.7 (cid:2) 1013 cm(cid:3)3 under a He 100-A and 0.45-l/min condition.
关键词： electron density,plasma temperature,emission spectroscopy,virtual vacuum interfaces,He plasma,cascade arc plasma sources,plasma windows,Ar thermal plasma
更新于2025-09-04 15:30:14
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Atomic layer etching of chrome using ion beams
摘要： In this study, two Cr atomic layer etching (ALE) methods have been applied for the precise control of Cr etching. The first one involves O radical adsorption followed by Cl+ ion desorption (ALE with chemical ion desorption; chemical anisotropic ALE), and the second one involves Cl/O radical adsorption followed by Ar+ ion desorption (ALE with physical ion desorption; physical anisotropic ALE). Their effects on Cr etch characteristics were also investigated. For both the ALE methods, saturated Cr etch depth/cycle of 1.1 and 1.5 ? /cycle were obtained for the chemical and physical anisotropic ALE, respectively, while maintaining near-infinite etch selectivities with various Si-based materials like silicon, silicon dioxide, and silicon nitride. The ALE technique can be used to precisely control the thickness of materials, including metals such as Cr, without any surface damage.
关键词： etch selectivity,adsorption,atomic layer etching,x-ray photoelectron spectroscopy,ion beam,chrome
更新于2025-09-04 15:30:14
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Study on the Synthesis of GO-AgNP Mixture Assisted by AgNP Based on UV-Vis, SEM-EDX, XRD, and FTIR
摘要： This study aims to determine the effect of silver nanoparticles (AgNP) towards graphene oxide-silver nanoparticles (GO-AgNP) formation using liquid sonication exfoliation (LSE) method. The synthesis results are characterized using UV-Vis spectroscopy, scanning electron microscope (SEM-EDX), X-ray diffraction (XRD), and Fourier transform infra-red (FTIR) spectroscopy. This research begins by making two type of solutions. The first solution is AgNO3 solution which is being varied in concentration, i.e.: 1 mM, 2 mM, 3 mM, and 4 mM. The second solution is the graphite solution. Via the LSE method, AgNO3 that has been heated into becoming AgNP solution is mixed with the graphite solution. The mixture is subjected to 6 hours of ultrasonication. From this study GO or rGO material has been produced through the assistance of AgNP solution by varying the concentration of the AgNO3 solution. The UV-Vis result for 4 mM concentration shows two absorbance peaks with wavelength values of 265 nm and 416.5 nm. This also leads to a redshift of the GO absorbance peak with a wavelength of 252 nm to 265 nm resulting in reduction of GO (rGO) material. The SEM results of GO-AgNP samples do not show the presence of AgNP granules corresponding to the EDX results showing that the oxygen element has the highest percentage. The XRD results are shown by comparing the diffraction patterns of the GO-AgNP sample and that of GO sample. Furthermore FTIR results indicate the presence of C-H alkanes, C=O bonds, and O-H bonds in the GO-AgNP samples.
关键词： GO,XRD,FTIR,UV-Vis spectroscopy,GO-AgNP,AgNP,SEM-EDX
更新于2025-09-04 15:30:14
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NIR spectroscopy research in the Ozaki group for the last 30 years
摘要： The purpose of this article is to introduce NIR spectroscopy research in the Ozaki group for the last 30 years. It might be interesting for some readers to know how and why our group pursued NIR spectroscopy for the last three decades. Perhaps, the readers can learn research purpose, research direction, strategy and tactics of NIR studies of our lab. For the last 30 years or so NIR spectroscopy has made fantastic progress in theory, instrumentation, spectral analysis, and application. Thus, the history of the Ozaki group strongly reflects the history of NIR spectroscopy. We have run after the rapid progress of NIR spectroscopy, and at the same time, probably we have created some novel advances of NIR spectroscopy.
关键词： NIR spectroscopy,research history,spectral analysis,instrumentation,Ozaki group
更新于2025-09-04 15:30:14
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2018) - Nagoya (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Experimental Characterization of Artificial Human Skin with Melanomas for Accurate Modelling and Detection in Healthcare Application
摘要： A preliminary investigation is carried out on the artificial human skin tissues with and without metastatic melanomas using Terahertz Time Domain Spectroscopy (THz-TDS). Both the refractive indexes and absorption coefficients of artificial skin with melanomas are higher than the normal artificial skin samples over the entire frequency range between 0.2 THz to 1.6 THz. The reason is that tumour cells degrade the in contraction of fibroblasts causing more water content malignant tissues. This study quantifies the impact of melanomas on the optical parameters of artificial skin tissue and can help in techniques that will diagnose and prevent tumours at the early stage.
关键词： artificial human skin,absorption coefficient,Terahertz Time Domain Spectroscopy,refractive index,melanomas
更新于2025-09-04 15:30:14
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Complementarity of Electronic and Vibrational Circular Dichroism Spectroscopy in Structure Determination of Vic-Amino Alcohols
摘要： There is no doubt that determination of the absolute configuration of isolated natural products or synthesized compounds remains one of the most important tasks in all fields of chemistry, biochemistry, structural biology and medicinal chemistry. This is unquestionably due to the fact that biological activity is closely related to the stereostructure of bioactive compounds. Therefore, access to methods allowing simple and primarily unequivocal determination of their absolute configuration (AC) and/or conformation is of particular significance. Such a role is at present fulfilled by chiroptical techniques. In the last two decades chiroptical spectroscopy has been one of the most rapidly developing areas of chiral analysis due to the availability of modern, highly specialized and dedicated to particular chiroptical techniques commercial instruments. Recent progress in ab initio simulations of chiroptical properties has also significantly contributed to the increase of the use of chiroptical spectroscopy as a stereochemistry probe [1]. It is generally accepted that combined experimental and theoretical analysis opens much broader application opportunities for chiroptical spectroscopy by giving theoretical basis to experimental results [1-4]. Moreover, utilization of multiple (at least two) chiroptical techniques increases the confidence level of the stereochemical assignment and is nowadays considered by many authors to be the best practice [1-5]. In this Editorial, we will focus on such a combined experimental and theoretical approach of electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) to determine the absolute configuration and conformation. We intend to demonstrate that both these chiroptical techniques are well cooperating and mutually complementary. Moreover, we want to show that the concerted use of the two methods clearly provides more definitive ACs although in many cases stereochemistry can be determined by using only a single chiroptical property. As a model compound for this study (1S,2R)-2-amino-1,2-diphenylethanol (1) with formula shown here below and representing vic-amino alcohols was chosen (Figure 1).
关键词： Electronic Circular Dichroism,Chiroptical Spectroscopy,Absolute Configuration,Vic-Amino Alcohols,Vibrational Circular Dichroism
更新于2025-09-04 15:30:14
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Effect of growth pressure on graphene direct growth on r-plane and c-plane sapphires by low-pressure CVD
摘要： Graphene was grown on both r-plane and c-plane sapphires by low-pressure chemical vapor deposition without using a metal catalyst. The growth pressure was systematically changed to investigate how the growth pressure effects the graphene growth. Consequently, it was found that the coverage of the graphene increased with increasing growth pressure on the r-plane sapphire while it decreased with increasing growth pressure on the c-plane sapphire. Raman spectroscopy and atomic force microscopy indicates that the growth layer is single-layer graphene on the r-plane sapphire while it is a bi-layer on the c-plane sapphire. Graphene is thought to grow on the r-plane sapphire simply in a two-dimensional nucleation mode. On the other hand, graphene tends to grow in the pits formed on the surface of the c-plane sapphire. The pits are thought to be produced by the oxygen desorption and have some catalytic effects.
关键词： sapphire,low-pressure CVD,atomic force microscopy,growth pressure,graphene,Raman spectroscopy
更新于2025-09-04 15:30:14
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Separation and Identification of Functional Groups of Molecules Responsible for Fluorescence of Biodiesel Using FTIR Spectroscopy and Principal Component Analysis
摘要： In order to separate and identify functional groups of molecules responsible for fluorescence compounds present in biodiesel, a column chromatography coupled with infrared spectroscopy and multivariate analysis was performed. A biodiesel sample was packed in a chromatographic column and the fractions obtained were used to perform the analyses. Before undergoing the separation process, the biodiesel sample was analyzed by light emitting diode (LED)-induced fluorescence and compared its spectrum with β-carotene and soybean oil patterns. The low cost and speed of analysis suggest that this technique can be used in the separation of biodiesel substances. The fluorescence emission spectra allowed identifying molecules such as β-carotene, in which the spectrum of its pattern exhibited fluorescence within a region ranging from 500 to 700 nm and chlorophyll molecules. When soybean oil is excited at around 405 nm, it features a fluorescent emission band within the region of 670 nm, which reveals the presence of chlorophyll. Infrared spectroscopy coupled with principal component analysis allowed to discriminate the fractions and to identify the functional groups of compounds present in the sample.
关键词： fluorescence,fluorophores,infrared spectroscopy,principal component analysis,biodiesel
更新于2025-09-04 15:30:14