Narrow Results

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.

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.

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.