Determining the Determining the Valence State of Lead Valence State of Lead in Compounds Using in Compounds Using PIXE PIXE

Andrew VoterAndrew Voter

Nuclear groupNuclear group

July 23, 2007 July 23, 2007

MotivationMotivation

Valence state is the charge on the Valence state is the charge on the metal ionmetal ion

Why is it important to know this?Why is it important to know this?

- Synthesis of new - Synthesis of new compounds leads to new compounds leads to new questions about chemical questions about chemical structure and functionstructure and function

Hope Ion Beam Hope Ion Beam Analysis Lab (HIBAL)Analysis Lab (HIBAL)

Accelerates ions Accelerates ions through a large through a large potential to high potential to high energiesenergies

Can accelerate Can accelerate protons or alpha protons or alpha particlesparticles

We observe what We observe what happens after the happens after the ions hit the targetions hit the target

Particle Induced X-ray Particle Induced X-ray Emission (PIXE)Emission (PIXE)

Accelerated protons Accelerated protons excite inner electron excite inner electron shells of the targetshells of the target

Other electrons fill Other electrons fill the gap and give off the gap and give off large amounts of large amounts of energy in the form of energy in the form of X-raysX-rays

Energy

Protons excite e-

from inner shells

e- Energy

Characteristic X-ray emitted

e-X-ray

Energy

Protons excite e-

from inner shells

e- Energy

Characteristic X-ray emitted

e-X-ray

Energy

Characteristic X-ray emitted

e-X-ray

These X-rays are detected; their energy These X-rays are detected; their energy identifies the elemental source, and the identifies the elemental source, and the number of x-rays identifies concentration number of x-rays identifies concentration

The GoalThe Goal

““Influence of Influence of chemical chemical environment on the environment on the analysis of analysis of PIXE/XRF spectra of PIXE/XRF spectra of samples containing samples containing various various compounds”compounds”11

i.e. peaks change i.e. peaks change (slightly)(slightly)

A Typical Lead PIXE Spectra

1Fazinic, S. et al.; XI Intl. Conf. on PIXE. May25-29, 2007.

L peakLβ peak

L

Energy

What causes this What causes this change? change? Valence state of element in Valence state of element in

compoundcompound Crystal structure of the compoundCrystal structure of the compound Cell parameters of the compoundCell parameters of the compound StatisticsStatistics Something else…Something else…

Preparation of Preparation of SamplesSamples

Compound mixed Compound mixed with organic binder with organic binder

Pellet pressing with Pellet pressing with hydraulic presshydraulic press

Pellet is then Pellet is then mounted onto a mounted onto a slide slide

Slide placed in PIXE Slide placed in PIXE chamberchamber

The ProcedureThe Procedure

Tested Cu, Mn, Pb Tested Cu, Mn, Pb compoundscompounds

Compounds Compounds appear sorted by appear sorted by valence statevalence state

Pb (0) metalPb (0) metal

PbOPbO2 2 (IV)(IV) Size effect too?Size effect too?

Energy

Future WorkFuture Work

Double blind test of unknown Double blind test of unknown element element

Testing compounds of more Testing compounds of more elementselements

(more Mn, Cr, (more Mn, Cr, Ru?) Ru?)

Publish results Publish results

Acknowledgements Acknowledgements

Dr. Graham PeasleeDr. Graham Peaslee Dr. Paul DeYoungDr. Paul DeYoung Dave DaughertyDave Daugherty Nuclear GroupNuclear Group R.E.A.C.H. ProgramR.E.A.C.H. Program Hope College Hope College NSFNSF