Y. Sasa

Quantitative analysis of ancient Egyptian pigments by external PIXE

Abstract Pigments painted on Egyptian excavations in the 18th Dynasty were analyzed successfully by external PIXE with the aid of the X-ray diffraction. A white pigment was composed of Mg 3 Ca(CO 3 ) 4 ; red: αFe 2 O 3 , αFeO·OH and AsS; pink: mixtures of white and red pigments; yellow: αFeO·OH and As 2 S 3 ; and blue: CaO·CuO·4SiO 2 .

Application of the external PIXE analysis to ancient Egyptian objects

Mural paintings with ∼20 × 25cm2 in size excavated in Egypt were analyzed by the external PIXE technique. Colored layers were stacked with white, yellow, red and black pigments in sequence, which were composed of Mg3Ca(CO3)4 (white), αFeO·OH and As2S3 (yellow), αFe2O3 (red) and soot (black), respectively. A single particle of As2S3 was also found from the yellow colored part, which glinted in the sun. A thin paraffin layer did not disturb the PIXE analysis, which was a part of reinforcement materials for ancient remains and was flowed out from a back side to a surface region.

Energy spectra of secondary electrons from Al induced by high speed He2+ and Ar12+ impact

Abstract Spectra of secondary electrons from Al produced by He2+ and Ar12+ ion impact (1.1 MeV/amu) were measured and compared with each other in the energy region below 170 eV. Ratios of secondary electron emission yields for Ar12+ impact to those for He2+ impact showed q2-proportionality in the high-energy region above 80 eV, but a prominent decrease in the energy region below 20 eV. It is proposed that this large reduction in the low energy region can be explained by a pronounced decrease in the creation of electron-hole pairs due to plasmon damping, together with the decrease in ionization cross sections of conduction electrons due to a correlation effect in high density ionization.

PIXE-induced XRF analysis for trace amounts of Mn, Cr, V and Ti in low-alloy steels

Abstract Trace amounts of Mn, Cr, V and Ti in low-alloy steels were analyzed by a nondestructive PIXE-induced XRF method. For exciting Mn most effectively among these elements, which is the most difficult element to be analyzed by PIXE, combined foils of Co and Fe were used as a primary target for X-rays. A method was used which subtracts a PIXE-XRF spectrum from a spectrum of steel with 99.998 mass% Fe in order to reduce contributions of inelastically scattered, or Raman scattered, Co Kα X-rays from Fe in the steels, which appear at the same energy region as the Mn Kα X-rays. This subtraction produced a significant improvement in the detection sensitivity for Mn, giving a minimum detection limit of 17 ppm.

Application of PIXE analysis to materials science

Abstract We have attempted to develop a simple and convenient data-processing procedure suited to PIXE analysis of industrial materials. We have demonstrated, with the use of reference samples of known chemical concentrations of minor of trace elements, that the continuous X-ray background can be successfully used to estimate total amounts of incident ions for quantitative trace elemental analysis, and that the conversion factors from X-ray intensities to elemental concentrations were common for all the elements detected.

Nickel Lα spectra measured by a high resolution particle induced X-ray emission (PIXE) spectrometer

Abstract The satellite spectra of Ni Lα X-rays induced by 21.0 MeV/amu N 2+ ion bombardment were measured using a high-resolution soft X-ray spectrometer which was specially designed for the chemical state analysis by PIXE. We succeeded in observing two distinguished satellite lines, whose energies were estimated by the use of a relativistic self-consistent field program. Relative intensities of the satellites observed here were also well reproduced by theoretical values estimated from the semiclassical approximation after correcting the X-ray selfabsorption. The satellites were confirmed to originate from the multiply ionized states with one L 3 and n M electron vacancies.

PIXE analysis of calcified tissues by use of a combined X-ray absorber

Abstract PIXE was applied to analyze salivary stones, whose major elements were calcium, phosphorus and oxygen. In order to detect elements with atomic number higher than that of Ca with a high sensitivity, a combined X-ray absorber composed of Nad was used which attenuated Ca Kα X-rays drastically. Trace elements such as S, Cl, Fe, Ni, Cu, Zn, Se, Br, Sr and I were detected from the salivary stones. Selenium in a high concentration was found for the first time in the salivary stones and/or living bodies.

Zn dopant analysis in GaAs

Abstract A trace amount of Zn in Zn-doped GaAs was analyzed with high sensitivity and accuracy by PIXE, i.e. 300 ppm with a detection limit of 20 ppm. For this purpose an absorber made of both Cu and Ga was used. A method subtracting a PIXE spectrum emitted from dopant-free GaAs from that of Zn-doped GaAs was useful for significant improvements in the reliability of the PIXE analysis.

Energy spectra of Al-LVV auger electrons induced by grazing angle incident fast heavy ion impact

Abstract Angular-resolved energy spectra of Al-LVV Auger electrons induced by impacts of N 6+ , Ar 46+ , Ar 12+ , and Xe 9+ with incident energies corresponding to 0.84–1.3 MeV/amu have been measured for two incident angles of 39° and 4° relative to the surface of the target. The energy of the Auger peak is found to be low for the 4° incidence compared with that for the 39° incidence. Such energy decrease becomes more significant as the atomic number of the projectiles increases. An emission angle dependence of the energy decrease is not observed. The mechanism for the energy decrease is tentatively discussed in terms of a surface effect.

Continuous backgrounds in heavy-ion induced X-ray emission

Abstract We report here continuous X-rays emitted from targets bombarded with Si3+ ion beams of 1.435 MeV/amu over the range of target-atomic number ZT = 6–29. It is shown that the production cross sections of continuous X-rays can be well scaled with a function of the product of the K-shell radius of the united atom and the minimum transfer momentum of the projectile while MO X-ray spectra are scaled with the K X-ray energy of the united atom. These continuous X-rays may be interpreted as bremsstrahlung produced from a united atom which is formed by a projectile ion and a target atom during collision; we call this radiation united-atomic bremsstrahlung. In consideration of this continuous background, we discuss utility of a trace element analysis with high energy heavy-ion beams especially for analysis of chemical states by using a crystal spectrometer.