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Chemical shifts of Kα_1,2 line of sulfur in marine sediments were measured with in-air high-resolution PIXE in order to examine the possibility of direct speciation of sulfur in such environmental substances. Change of chemical states of sulfur along the depth in the sediments was observed. Oxidation of the sediment samples by air was also examined. Problems to be improved for exact speciation are discussed.

The alignment effect on the L-shell ionization of Nb atom (Z=41) by 0.84MeV, 1.38MeV and 2.92MeV proton impact was investigated. The polarization of L_ℓ X-rays emitted from the aligned niobium target was measured with the crystal spectrometer combined with a position sensitive proportional counter. The experimental values of the degree of alignment A₂ were compared with the prediction of PWBA theory. It results that the experimental value of A₂ in 1.38MeV proton impact was much larger than the theoretical one, and A₂ of 0.84MeV almost coincides with that of 2.92MeV.

A narrow entrance slit was attached to an in-air high-resolution PIXE system composed of a flat analyzing crystal and a position-sensitive proportional counter. Chemical shift measurements were carried out for Si, P and S Kα_1,2 lines from various sample targets. The precision of measurements is much improved compared with that obtained by the position-sensitive crystal spectrometer system without the entrance slit. The new system equipped with the entrance slit does not require exact sample positioning. It is applicable to non-flat targets. Chemical shift measurements are also possible while moving the targets.

The feasibility of RIKEN high-resolution PIXE system for direct chemical state analysis of 3d transition elements was examined. Kβ spectra of Cr and Fe from several compounds were measured in air at atmospheric pressure using a crystal spectrometer consisting of a position-sensitive proportional counter and a curved crystal in v. Hamos geometry. Fine structures which reflect the chemical states of Cr and Fe were well recognized with the measuring time of tens minutes.

In this paper, we have developed a wavelength dispersive X-ray spectrometer microparticle-induced X-ray emission (WDX-$\mu$-PIXE) system combining a microbeam system with high spatial resolution and wavelength dispersive X-ray (WDX) spectrometry with high-energy resolution for chemical state mapping. A Von Hamos geometry was used for the WDX system to achieve higher detection efficiency and energy resolution. The system consists of a curved crystal and a CCD camera. The WDX system was installed in a newly developed microbeam system. The energy resolution of the WDX system was 0.67 eV for $\text{Si-}{K}_{\alpha 1}$ (1740 eV). $\text{Si-}{K}_{\alpha 1,2}$ and $\text{Si-}{K}_{\beta }$ X-ray spectra from various Si compounds were measured and chemical shifts related to chemical states were clearly observed. The system was applied to the chemical state analysis of clay particles. After elemental mapping of the clay particles using a conventional $\mu$-PIXE system with a Si(Li) detector, particles to be analyzed were selected and analyzed sequentially with the WDX system. $\text{Si-}{K}_{\beta }$ spectra from clay particles were obtained. The microscopic spatial distribution of elements and chemical state of the clay particles were sequentially measured with high energy and spatial resolution using a microbeam.

A charge-division, position-sensitive proportional counter with a carbon-fiber anode and its associated signal processor has been developed. This counter is very small in volume with a simple structure and vacuum proof. The spatial resolution of 0.36 mm was achieved under a gas pressure of 1.7×10⁵ Pa. A correlation factor between the position and the channel number was measured to be 0.97, indicating good linearity of the system. The detector was combined with a crystal spectrometer in order to measure spectra of particle-induced characteristic X rays. Energy resolutions measured at Si K_α (1.74 keV) and Fe K_α (6.4 keV) X rays are 4 and 34 eV, respectively.

A soft X-ray crystal spectrometer designed for chemical state analysis by PIXE is described. A windowless, microchannel plate (MCP) electron multiplier combined with a photodiode array was used as a position-sensitive detector for X-rays diffracted by a plane crystal. The spectrometer was tested for Al Kα and Fe L X-ray spectra induced by 15 MeV N²⁺ ion impact. An energy resolution (FWHM) of 1.5 eV for the 1487 eV Al Kα_{1, 2} line was obtained for metallic Al, and satellite structures of Al Kα arising from multiply ionized states were well resolved. Fe L X-ray spectra were measured for Fe₂O₃ and metallic Fe. Chemical effects were clearly recognized in the Fe Lα/Lβ intensity ratio and in the intensity distributions of their multiple vacancy satellites.

We describe characteristics of high-resolution, wavelength-dispersive crystal spectrometers equipped with a different type of position sensitive X-ray detectors: PSPC, CCD, IP and MCP. Utilities of these position sensitive spectrometers in PIXE experiments are demonstrated by referring several recent topics of elemental analysis, chemical state analysis and a study on sample charging.

A position-sensitive proportional counter (PSPC) for a wavelength-dispersive crystal spectrometer system has been constructed for high-resolution PIKE experiments in atmospheric air. This PSPC has seven resistive wire anodes. Each anode operates as one PSPC. Pulses from the anodes are converted into digital signals with a 512 × 7 channel charge-division analyzer. We can simultaneously obtain seven spectra. A computer software converts this 2D data set into one spectrum after adjusting the offset channels and conversion factors. The spatial resolution of this detector is somewhat larger than that of our single PSPC system previously developed, while its counting efficiency is seven times higher than that of the single one.