Chemical state speciation by resonant Raman scattering

Abstract

In the resonant Raman scattering (RRS) process the emitted photon exhibits a continuous energy distribution with a high energy cutoff limit. This cutoff energy depends on the chemical state of the element under examination. In the present work, the possibility of identifying the chemical state of V atoms by employing RRS spectroscopy with a semiconductor Si(Li) detector is investigated. A proton induced Cr Kα x-ray beam was used as the incident radiation, having a fixed energy lower than the V K-absorption edge. The net RRS distributions extracted from the energy dispersive spectra of metallic V and its compound targets were simulated by an appropriate theoretical model. The results showed the possibility of employing RRS spectroscopy with a semiconductor detector for chemical speciation studies.

Influence of near-edge processes in the elemental analysis using X-ray emission-based techniques

“…This energy change ( E b ) may be of the order of few eV in the low-and medium-Z elements. The K shell binding energy of 13 Al in Al 2 O 3 and 14 Si in SiO 2 , 24 Cr in Cr 2 O 3 and (CrO 4 ) 2− , were measured to be higher by 5.9 and 8.0 eV [29], 7 and 15 eV [31], respectively, than that in the metallic state. If the photon energy, E in , is higher by few eV than an ionization threshold of the attenuator atom in elemental form, it exhibits XAFS.…”

Resonant Raman scattering of polarized and unpolarized x-ray radiation from Mg, Al, and Si

“…"Demokritos", Athens. The principle of the proton-induced XRF technique has been previously discussed and applied toward fundamental as well as analytical x-ray spectrometry studies over lowenergy particle accelerators facilities [16][17][18][19]; that is, as a few-MeV high current proton beam irradiates a thick pure primary target, the induced characteristic lines form an intense x-ray source with selectable energy to be used for further x-ray-related studies. The two-level chamber ( Fig.…”

“…However, when low-resolution spectrometers are employed, this fine structure is averaged out and a boxlike function can be safely used by assuming a mean energy (T e ) for the excited electrons as previously discussed. By substituting g 1s,2p and dg K dT e [16,31] and grouping the constant terms, the differential RRS cross section can be written as…”

“…Up until now several studies have been accomplished related to the systematic determination of the RRS cross sections for transition metals and rare-earth elements by means of synchrotron radiation, x-ray tubes coupled with crystal monochromators, and radioactive or proton-induced x-ray beams [3,4,[16][17][18][19][20][21][22][23][24][25][26]. Nevertheless, despite the important role played by low-Z elements such as Mg, Al, and Si in new materials (e.g., as impurities in silicon wafers) studies of these elements have been rather scarce.…”

Proton induced quasi-monochromatic x-ray beams for soft x-ray spectroscopy studies and selective x-ray fluorescence analysis

“…The advantages for such an x-ray source are mainly related to the high inner shell ionization cross sections of heavy ions, and most important with the very low emission, compared to electrons, of bremsstrahlung radiation as the ions decelerate into matter resulting in an improved peak to background ratio. 1 The concept of the proton-induced monochromatic x-ray beams [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] has been utilized in the past in various spectroscopy and analytical studies related with the determination of impurities or minor elements in pure metal matrices, [8][9][10][11][12] as well as for inelastic x-ray scattering experiments in experimental conditions (exciting x-ray beam energy, atomic number of the target element) that favour the study of x-ray resonant Raman scattering (RRS) [13][14][15][16] and more recently for the production of soft keV micro-focused x-rays for single cell irradiation allowing for a more consistent dose delivery. 19 Here, through the development of an integrated x-ray spectroscopy end station, we describe the dynamic utilization of the advantages of proton-induced x-ray beams when used for soft x-ray spectroscopy applications and especially for XRF analytical purposes.…”