X-ray photoelectron spectroscopy study on GaN crystal irradiated by slow highly charged ions

We utilize slow highly charged ions of Xeq+ and Pbq+ to irradiate GaN crystal films grown on sapphire substrate, and use X-ray photoelectron spectroscopy to analyze its surface chemical composition and chemical state of the elements. The results show that highly charged ions can etch the sample surface obviously, and the GaN sample irradiated by highly charged ions has N depletion or is Ga rich on its surface. Besides, the relative content of Ga-Ga bond increases as the dose and charge state of the incident ions increase. In addition, the binding energy of Ga 3d(5/2) electrons corresponding to Ga-Ga bond of the irradiated GaN sample is smaller compared with that of the Ga bulk material. This can be attributed to the lattice damage, which shifts the binding energy of inner orbital electrons to the lower end.

低速高电荷态重离子辐照的GaN晶体表面X射线光电子能谱研究；X-ray photoelectron spectroscopy study on GaN crystal irradiated by slow highly charged ions

利用低速高电荷态Xeq+和Pbq+离子对在蓝宝石衬底上生长的GaN晶体膜样品进行辐照,并利用X射线光电子能谱(XPS)对样品表面化学组成和元素化合态进行了分析.结果表明,高电荷态离子对样品表面有显著的刻蚀作用;经高电荷态离子辐照的GaN样品表面氮元素贫乏而镓元素富集;随着入射离子剂量和所携带电荷数的增大,Ga—Ga键相对含量增大;辐照后,GaN样品中Ga—Ga键对应的Ga3d5/2电子的束缚能偏小,晶格损伤使内层轨道电子束缚能向低端方向偏移.

Quantitative analysis analysis of element concentration in Al alloy by using laser-induced breakdown spectroscopy

Laser-induced breakdown plasma is produced by using Q-switched Nd: YAG laser operating at 532 nm, which interacts with the Al alloy sample target in air. The spectral lines in the 230-440 nm wavelength range have been identified, and based on the calibration-free method, the mass concentration of Al alloy are obtained, which is in good agreement with the standard value of the sample.

A Semi-Quantitative Analysis of Essential Micronutrient in Folium Lycii Using Laser-Induced Breakdown Spectroscopy Technique

In this paper, the capabilities of laser-induced break down spectroscopy (LIBS) for rapid analysis to multi-component plant are illustrated using a 1064 nm laser focused onto the surface of folium lycii. Based on homogeneous plasma assumption, nine of essential micronutrients in folium lycii are identified. Using Saha equation and Boltzmann plot method electron density and plasma temperature are obtained, and the irrelative concentration (Ca, Mg, Al, Si, Ti, Na, K, Li, and Sr) are obtained employing a semi-quantitative method.

Influence of Laser Wavelength on Laser-induced Breakdown Spectroscopy Applied to Semi-Quantitative Analysis of Trace-Elements in a Plant Sample

Laser-induced breakdown spectroscopy (LIBS) as a powerful analytical technique is applied to analyze trace-elements in fresh plant samples. We investigate the LIBS spectra of fresh holly leaves and observe more than 430 lines emitted from 25 elements and molecules in the region 230-438 nm. The influence of laser wavelength on LIBS applied to semi-quantitative analysis of trace-element contents in plant samples is studied. The results show that the UV laser has lower relative standard deviations and better repeatability for semi-quantitative analysis of trace-element contents in plant samples. This work may be helpful for improving the quantitative analysis power of LIBS applied to plant samples.

Molecular vibration spectroscopy study of irradiation effect in C-60 films induced by low energy ion

Irradiation effect in C-60 films induced by 170 keV B ion was investigated by means of Fourier transform infrared (FTIR) and Raman spectroscopies. The damage cross section sigma and the effective damage radius R are deduced from the experimental data of all four IR active modes and evident four Raman active modes of C-60 molecule. The differences on irradiation sensitivity and structural stability of the different active modes of C-60 molecule are compared. The results indicate that T-1u (4) of infrared active mode and A(g) (1) of Raman active mode are most sensitive for B ion irradiation. On the other hand T-1u (2) of infrared active mode and H-g (3) of Raman active mode are comparatively stable under B ion irradiation. (C) 2010 American Institute of Physics. [doi:10.1063/1.3512968]

Rotamers of m-aminophenol cation studied by mass analyzed threshold ionization spectroscopy and theoretical calculations

The vibrationally resolved spectra of selected rotamers of m-aminophenol have been recorded by mass analyzed threshold ionization spectroscopy in connection with two-color resonant two-photon excitation scheme. The adiabatic ionization energies of the cis and trans rotamers are 61460 +/- 5 and 61734 +/- 5 cm(-1), respectively. The frequencies of modes 1 (breathing) and 18a (in-plane CH bending) are measured to be 744 and 1097 cm(-1) for the cis, and 736 and 1104 cm(-1) for the trans rotamer, respectively. This indicates that different orientation of the OH with respect to the NH2 substituent only slightly influences these two modes. (C) 2004 Elsevier B.V. All rights reserved.

Adsorption and reaction of thiophene and H2S on Mo2C/Al2O3 catalyst studied by in situ FT-IR spectroscopy

The reactions of both thiophene and H2S onMo(2)C/Al2O3 catalyst have been studied by in situ FT-IR spectroscopy. CO adsorption was used to probe the surface sites of Mo2C/Al2O3 catalyst under the interaction and reaction of thiophene and H2S. When the fresh Mo2C/Al2O3 catalyst is treated with a thiophene/H-2 mixture above 473 K, hydrogenated species exhibiting IR bands in the regions 2800-3000 cm(-1) are produced on the surface, indicating that thiophene reacts with the fresh carbide catalyst at relatively low temperatures. IR spectra of adsorbed CO on fresh Mo2C/Al2O3 pretreated by thiophene/H-2 at different temperatures clearly reveal the gradual sulfidation of the carbide catalyst at temperatures higher than 473 K, while H2S/H-2 can sulfide the Mo2C/Al2O3 catalyst surface readily at room temperature (RT). The sulfidation of the carbide surface by the reaction with thiophene or H2S maybe the major cause of the deactivation of carbide catalysts in hydrotreating reactions. The surface of the sulfided carbide catalyst can be only partially regenerated by a recarburization using CH4/H-2 at 1033 K. When the catalyst is first oxidized and then recarburized, the carbide surface can be completely reproduced.

Structure and acidity of Mo/H-MCM-22 catalysts studied by NMR spectroscopy

A comprehensive study on physical and chemical properties of Mo/MCM-22 bifunctional catalysts has been made by using combined analytic and spectroscopic techniques, such as adsorption, elemental analysis, and Xe-129 and P-31 NMR of adsorbed trialkylphosphine oxide probe molecules. Samples prepared by the impregnation method with Mo loadings ranging from 2-10 wt.% have been examined and the results are compared with that obtained from samples prepared by mechanical mixing using MoO3 or Mo2C as agents. Sample calcination treatment is essential in achieving a well-dispersed metal species in Mo/MCM-22. It was found that, upon initial incorporation, the Mo species tend to inactivate both Bronsted and Lewis sites locate predominantly in the supercages rather than the 10-membered ring channels of MCM-22. However, as the Mo loading exceeds 6 wt.%, the excessive Mo species tend to migrate toward extracrystalline surfaces of the catalyst. A consistent decrease in concentrations of acid sites with increasing Mo loading < 6 wt.% was found, especially for those with higher acid strengths. Upon loading of Mo > 6 wt.%, further decreases in both Bronsted and Lewis acidities were observed. These results provide crucial supports for interpreting the peculiar behaviors previously observed during the conversion of methane to benzene over Mo/MCM-22 catalyst under non-oxidative conditions, in which an optimal performance was achieved with a Mo loading of 6 wt.%. The effects of Mo incorporation on porosity and acidity features of the catalyst are discussed. (C) 2004 Published by Elsevier B.V.

State-to-state dynamics of elementary chemical reactions using Rydberg H-atom translational spectroscopy

In this review, a few examples of state-to-state dynamics studies of both unimolecular and bimolecular reactions using the H-atom Rydberg tagging TOF technique were presented. From the H2O photodissociation at 157 nm, a direction dissociation example is provided, while photodissociation of H2O at 121.6 has provided an excellent dynamical case of complicated, yet direct dissociation process through conical intersections. The studies of the O(D-1) + H-2 --> OH+H reaction has also been reviewed here. A prototype example of state-to-state dynamics of pure insertion chemical reaction is provided. Effect of the reagent rotational excitation and the isotope effect on the dynamics of this reaction have also been investigated. The detailed mechanism for abstraction channel in this reaction has also been closely studied. The experimental investigations of the simplest chemical reaction, the H-3 system, have also been described here. Through extensive collaborations between theory and experiment, the mechanism for forward scattering product at high collision energies for the H+HD reaction was clarified, which is attributed to a slow down mechanism on the top of a quantized barrier transition state. Oscillations in the product quantum state resolved different cross sections have also been observed in the H+D-2 reaction, and were attributed to the interference of adiabatic transition state pathways from detailed theoretical analysis. The results reviewed here clearly show the significant advances we have made in the studies of the state-to-state molecular reaction dynamics.

On the surface sites Of MOP/SiO2 catalyst under sulfiding conditions: IR spectroscopy and catalytic reactivity studies

The surface sites of MoP/SiO2 catalysts and their evolution under sulfiding conditions were characterized by IR spectroscopy using CO as the probe molecule. The HDS activities of thiophene were measured on the MoP/SiO2 catalyst that was subjected to different sulfidation and reactivation pretreatments. Cus Modelta+ (0 < delta less than or equal to 2) sites are probed on the surface of fresh MoP/SiO2 by molecularly adsorbed CO, exhibiting a characteristic IR band at 2045 cm(-1). The surface of MoP/SiO2 is gradually sulfided in HDS reactions, as revealed by the shift of the IR band at 2045 to ca. 2100 cm(-1). Although the surface of a MoP/SiO2 catalyst becomes partially sulfided, the HDS activity tests show that MoP/SiO2 is fairly stable in the initial stage of the HDS reaction, providing further evidence that molybdenum phosphide is a promising catalytic material for industrial HDS reactions. Two kinds of surface sulfur species are formed on the sulfided catalyst: reversibly and irreversibly bonded sulfur species. The MoP/SiO2 catalyst remains stable in the HDS of thiophene because most sulfur species formed under HDS conditions are reversibly bonded on the catalyst surface. A detrimental effect of presulfidation on the HDS activity is observed for the MoP/SiO2 catalyst treated by H2S/H-2 at temperatures higher than 623 K, which is ascribed to the formation of a large amount of the irreversibly bonded sulfur species. The irreversibly sulfided catalyst can be completely regenerated by an oxidation and a subsequent reduction under mild conditions. (C) 2003 Elsevier Inc. All rights reserved.