Xray Fluorescence Analysis A Somogyi ESRF A Iida

X-ray Fluorescence Analysis A. Somogyi (ESRF) A. Iida (KEK-PF) K. Sakurai (NIMS, Tsukuba) T. Ohta (U. Tokyo)

What happens by core hole creation? K K L M X-ray Fluorescence L M Auger electron emission

How can we create core holes? • X-rays, Electrons, Ions which have higher energy than the core electron ionization energies. • Electrons and ions produces many peaks with multiple excitations. X-ray excitation is preferable. • Now, X-ray fluorescence analysis by X-ray excitation is a standard technique for trace element alalysis.

How is the Trace Characterization important? Bio-medical Industrial LSI ? Social Environmental ? ?

Why synchrotron radiation x-rays ? • Higher intensity higher sensitivity • Energy tunability Make the analysis easier, chemical state analysis • Polarizablity Reduce background • Directionality applicable to tiny sample • Spectromicroscopy, Imaging

Synchrotron Radiation excited X -ray fluorescence Analysis Advantages of XRF elemental analysis • Non-destructive • multi-elemental analysis • environmental condition • high accuracy • wide dynamic range SR • High sensitivity ng=>fg, ppm=>ppb • Chemical state analysis • Micro-beam analysis mm=> mm • Total reflection analysis 1015 atoms/cm 2=>108 atoms/cm 2

Total-refection X-Ray Fluorescence ( TXRF ) Reduction of scattering background from the substrate(1) Critical Angle Si ( Li ) Detector Sample

Total-refection X-Ray Fluorescence ( TXRF ) Reduction of scattering background from the substrate (2) SR (horizontally polarized beam) Fluorescent X-rays IS IF Detector r R Scattered X-rays

Comparison of S/N and S/B ratios Laboratory source Continuum excitation Refl. /Trans. Mirrors Monochromatic excitation Sample: chelete resin beads

How to analyze X-Ray Fluorescence Wavelength-dispersive vs. energy-dispersive Energy-dispersive electronic signal processing Wavelength-dispersive 2 dsinq=l Energy crystal MCA solar-slit semiconductor/ superconductor detector gas/scintillation detector Energy

Chemical Characterization by X-ray Fluorescence Spectra v. Qualitative and quantitative analysis vin terms of XRF Si ( Li ) detector Intensity changes Single-crystal spectrometer Chemical shifts Profile changes and other fine structures Satellite lines Double-crystal spectrometer

Chemical Shifts and Profile Changes High resolution X-ray spectrometry KMn. O 4 K 2 Mn. O 4 Mn green Mn. O 2 Mn 2 O 3 Mn. O Intensity ( normal ised ) Mn. Ka 1 0. 2 Mn. Ka 2 0. 1 0 0 10 20 Energy ( e. V ) ( + 5860 e. V ) 30 40 50 Prof. Y. Gohshi

Selectively Induced X-Ray Emission Using Edge Shifts Use of tunable monochromatic synchrotron source EL EH K. Sakurai ~1988 Fe 2 O 3 Fe. O

Synchrotron X-Ray Microbeam side view Kirkpatrick-Baez Optics top view sample Slit 1 Slit 2 SR sample IC IC Double crystal Multilayer monochromator Beam size 5~6 m 2 (1 m min) Photon Flux(Max) 1010 (Multilayer) 108 (DXM)

Application to criminology • A serious case of murder happened in a small town in Japan in 1999. • White arsenic(arsenic oxide) was mixed in curry and 5 kids died of arsenic poisoning. • No wittness and no confession, only presumptive evidence • XFS technique works effectively.

XFS of white arsenic produced in various countries As Ag Sb Sb Bi Korea China Spectral patterns from two samples agree with each other! Mexico X-ray energy(ke. V)

Plan View of Beamline 40 XU at SPring-8 Experimental hutch Optics hutch HALL K-B mirrors SR Spectrometer RING ID Gap 12 mm N N S S Helical Undulator (Distance from the source) 55 m 50 m 45 m 40 m 35 m

From Energy-dispersive to Wavelength-dispersive Spectrometer To further upgrade signal to background ratio Energy-dispersive TXRF Si(Li) Detector X-ray Sample Wavelength-dispersive TXRF Scintillator detector Analyzing Crystal (Johansson) X-ray Sample Substrate Advantages Large solid angle (High detection efficiency) Advantages Collecting whole XRF spectra simultaneously High energy-resolution Disadvantages Good signal to background ratio Low energy-resolution Limitation of counting-rate Scattering background Disadvantages Low detection-efficiency

Design Considerations Flexibility and feasibility for practical analytical applications SR Curved Crystal Johansson Ge (220) 4 axes for scanning X-ray energy Entrance Slit Receiving Slit Vac. chamber 4 axes for alignment and positioning of the sample Detector Sample Rowland Circle R=120 mm ( flexible )

Compact Johansson X-ray Fluorescence Spectrometer He gas Ionization chamber Crystal analyzer Ge (220) Johansson SR Detector Vac. chamber Sample positioning stages

Performance of the Spectrometer Feasibility for the analysis of trace elements in small samples Coal Fly Ash (NIST SRM-2690) Lily Pollen (20 particles. ) 100 m 35 mm (300 ppm) Capillary Powders adhered to glue sphere (~0. 5 mm) (5800 ppm) FWHM 7. 2 e. V (67 ppm) Glass Capirally

WD-TXRF Spectra for Trace Elements in Micro Drop Significant enhancement of signal to background ratio Sample Fe, Ni, Co 20 ppb 0. 1 l X-ray 　5 sec/point　 Substrate FWHM 7. 06 e. V FWHM 6. 62 e. V FWHM 5. 71 e. V

Performance of Wavelength-Dispersive TXRF ppt level detection limit with less than 10 e. V energy Calibration curve Ni 1 ppb-0. 1 l liquid drop 13536 counts 　　/20 sec FWHM 7 e. V 196 counts 　　/20 sec Detection Limit of Absolute amount Concentration solution of 0. 1 l Ni in 0. 1 l solution Ni 0. 31 fg 3. 1 ppt

Summary Towards ppt chemistry Downsized wavelength depressive XRF spectrometer is effective to enhance both detection efficiency and energy resolution. ~10 -16 g ~10 -12(ppt) For 0. 1 ml 10 -3 Trace chemical characterization using Kb spectra Concentration ( g/g ) Reducing scattering background as well as parasitic X-rays due to contamination is extremely important. Conventional XRF 10 -6 (ppm) AAS 10 -9 (ppb) Conventional TXRF Present detection limit (SR-WD TXRF) ICP-MS 10 -12 (ppt) 10 -15 (fg) 10 -12 10 -9 (pg) (ng) Absolute amount ( g ) 10 -6 ( g)

Conclusions SR-X-ray XRF technique is very powerful. • Low detection limit down to fg, ppt level • applicable to samples of limited size • well analyzed due to energy tunability and high energy resolution • Development of XRF imaging • Combination with different micro techniques (XRD, XANES and EXAFS)