Post on 14-Jan-2016
description
X-ray spectroscopy
Andrew Preston
andrew@preston.co.nz
Outline of proceedings
1. Synchrotrons
2. Beamlines
3. Advantages/Applications
4. How to get access
1. Synchrotrons
What is a synchrotron?
• A big circle…
• …which accelerates charged particles…
• …which radiate light…
• …which we use
It’s a light source!
A very useful light source
• Very bright– Millions of times brighter than x-ray tubes
• Very colourful– Energies from infrared to hard x-ray
• Highly polarized– linear or circular
• Great time resolution– Pulses of nanosecond duration
• Key point: new uses, improves other uses
Uses
• Biosciences
• Medicine
• Environmental sciences
• Agriculture
• Minerals exploration
• Advanced materials
• Engineering
• Forensics
Light sources around the world
NSLS (New York)
Maxlab (Sweden)
Australian synchrotron
Australian synchrotron
• Beamlines– Protein crystallograppy– Infrared spectroscopy– Soft x-ray spectroscopy– X-ray absorption spectroscopy– Powder diffraction
Australian synchrotron
• Beamlines under construction– Small and wide angle scattering– Protein micro-crystal and small moleculte
XRD– Microspectroscopy– Imaging and theray
Experiment
2. Beamlines
Light source
• Generate light (synchrotron)
• Isolate particular colour (monochromator)
• Conduct experiment
3. Advantages
Atom specific
Ef
Empty
Filled
Very bright
X-ray absorption
• XAS, XANES, NEXAFS, EXAFS
• Probe the unoccupied states around an atom
XAS
Band structure of ZnO from resonant x-ray emission spectroscopy
Preston et al. Phys. Rev. B 78, 155114 (2008)
Ef
• XPS, ARPES
• Photoelectric effect
• Measure kinetic energy of emitted electrons
Photoelectron spectroscopy
Empty
Filled
XPS/ARPES
• Measure the total density of states around an atom
• Surface state effects
• ARPES– resolve momentum of emitted electrons
ARPES
Origin of the metallic properties of boron-doped diamond
Yokoya et al. Nature 438, 647 (2005)
X-ray diffraction
• Similar to conventional XRD
• High flux– Better signal:noise ration
• High resolution– Angle/time
Highly oriented polythiophene thin-film transistors
Kline et al. Nat. Mat. 5, 222 (2006)
4. How to get access
• Apply!
• Apply!!
• Apply!!!
• New Zealand Synchrotron Group Ltd.– http://www.synchrotron.rsnz.org/user/
New Zealand Synchrotron Group
• Your university is a shareholder
• Designed to encourage use
• Two types of access– Merit (50%)– Preferred (30%)
• Can you apply?– YES!
References
• Tour of the ALS– http://www.youtube.com/watch?v=iEHWQv7b-Cw
• Light sources– http://www.lightsources.org/
• Australian synchrotron– http://www.synchrotron.org.au
• New Zealand Synchrotron Group Ltd.– http://www.synchrotron.rsnz.org/
• X-ray data booklet– http://xdb.lbl.gov/