Transcript
Page 1: X-ray spectroscopy Andrew Preston andrew@preston.co.nz

X-ray spectroscopy

Andrew Preston

[email protected]

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Outline of proceedings

1. Synchrotrons

2. Beamlines

3. Advantages/Applications

4. How to get access

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1. Synchrotrons

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What is a synchrotron?

• A big circle…

• …which accelerates charged particles…

• …which radiate light…

• …which we use

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It’s a light source!

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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

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Uses

• Biosciences

• Medicine

• Environmental sciences

• Agriculture

• Minerals exploration

• Advanced materials

• Engineering

• Forensics

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NSLS (New York)

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Maxlab (Sweden)

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Australian synchrotron

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Australian synchrotron

• Beamlines– Protein crystallograppy– Infrared spectroscopy– Soft x-ray spectroscopy– X-ray absorption spectroscopy– Powder diffraction

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Australian synchrotron

• Beamlines under construction– Small and wide angle scattering– Protein micro-crystal and small moleculte

XRD– Microspectroscopy– Imaging and theray

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Experiment

2. Beamlines

Light source

• Generate light (synchrotron)

• Isolate particular colour (monochromator)

• Conduct experiment

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3. Advantages

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Atom specific

Ef

Empty

Filled

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Very bright

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X-ray absorption

• XAS, XANES, NEXAFS, EXAFS

• Probe the unoccupied states around an atom

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XAS

Band structure of ZnO from resonant x-ray emission spectroscopy

Preston et al. Phys. Rev. B 78, 155114 (2008)

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Ef

• XPS, ARPES

• Photoelectric effect

• Measure kinetic energy of emitted electrons

Photoelectron spectroscopy

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XPS/ARPES

• Measure the total density of states around an atom

• Surface state effects

• ARPES– resolve momentum of emitted electrons

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ARPES

Origin of the metallic properties of boron-doped diamond

Yokoya et al. Nature 438, 647 (2005)

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X-ray diffraction

• Similar to conventional XRD

• High flux– Better signal:noise ration

• High resolution– Angle/time

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Highly oriented polythiophene thin-film transistors

Kline et al. Nat. Mat. 5, 222 (2006)

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4. How to get access

• Apply!

• Apply!!

• Apply!!!

• New Zealand Synchrotron Group Ltd.– http://www.synchrotron.rsnz.org/user/

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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!

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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/


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