Post on 13-Jan-2016
description
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