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![[School of Physics - Optics Group]](http://optics.ph.unimelb.edu.au/its1.gif)
Christopher T. Chantler, Professor, FAIP |
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School of Physics (Room 505) Cnr Elgin St / Swanston St [Building 192] University of Melbourne, Parkville, Victoria, 3010, AUSTRALIA Phone: +61 (0)3 8344 5437 (Office, Room 505, 5th floor) Fax: +61 (0)3 9347 4783 URL: http://optics.ph.unimelb.edu.au/~chantler
Hollywood Senior High School, Perth, Western Australia 1975 - 1979
BSc (Hons 1) University of Western Australia, 1980 - 1984.
D. Phil. Exeter College, Oxford University 1985 - 1990.
Prizes:
International JARI Enterprise Award by IRPS - for Outstanding work in the radiation sciences,
the nature of the research being recognised to be of a leading and challenging nature- 2006
David Syme Research Prize for - original research making an important contribution to the fields of Biology,
Chemistry, Geology or Physics - by an Australian researcher (awarded 16 May 2007) 2006
Lindemann Fellowship of the English-Speaking Union of the Commonwealth 1991-1992
St Anne's College Drapers' Company Junior Research Fellowship October 1989-1991
Shell Australia Postgraduate Scholarship for Science and Engineering 1985-88
Lady James Prize (Physical Science, UWA) 1983 (shared)
Digby-Fitzhardinge Memorial Prize for Physics (UWA) 1982.
Citations - for one of the best five works done at one of the APS sectors - for 2000,
in independent experiments on beamlines 1-ID and 12. Citation (APS Forefront 2001)
for outstanding research of the past year (2001) for beamline 2-ID-B, Paterson et al., pp178-180
X-ray Optics and Atomic Physics: Theory and Experiment
XAFS, XANES and Condensed Matter Science: Theory and Experiment
The X-ray Extended Range Technique for high-accuracy absorption and scattering measurement
Non-destructive Measurement of Nanoroughness
Measurement and Theory of the Inelastic Mean Free Path of the Electron
Powder Diffraction and X-ray Crystallography
Applications to Chemistry, Earth Sciences, Biology and Organometallics
QED explains how light interacts with matter and is fundamental to most of the technology we use today.
Quantum Electrodynamics is one of the two best-tested theories in physics and science. It is the most trusted example of a Quantum Field Theory in practice. Yet certain problems in its formulation lead people like Roger Penrose to assume that there are fundamental flaws in the theory. Our experiments at the cutting edge may reveal such an inadequacy, by being more sensitive to important terms and interactions than other available tests. Coming experiments can test alternate competing theories. QED is the primary explanation of the interaction of light and charge, and is fundamental to much of the physics which we assume and rely on in the world today. Experimental and theoretical developments in 1998 - 2008 are questioning the current theoretical approaches. Can hints of string theory, extra dimensions, or other formulations be found in atoms?I have pursued precision tests of Quantum Electrodynamics in atomic systems, and in a series of international collaborations have produced several high-precision measurements of QED in the medium-to-high Z regime. I have been involved in the development of X-ray specroscopy on the novel Electron Beam Ion Trap devices, in collaborations primarily at NIST. I have worked on few-electron physics for 20 years and have extensive experience with investigations at accelerators in Oxford, GSI, Lawrence Berkeley Laboratory and Argonne. We have performed the most precise measurements of the resonance lines of a helium-like ion in the Z=19-31 range, which allows sensitivity to two-electron QED effects and excited-state QED effects.
See
17. H. F. BEYER, K. D. FINLAYSON, D. LIESEN, P. INDELICATO, C. T. CHANTLER, R. D. DESLATTES, J. SCHWEPPE, F. BOSCH, M. JUNG, O. KLEPPER, W. KONIG, R. MOSHAMMER, K. BECKERT, H. EICKHOFF, B. FRANZKE, A. GRUBER, F. NOLDEN, P. SPADTKE, M. STECK, X-ray transitions associated with electron capture into bare dysprosium, J. Phys. B26 (1993) 1557-1567.
24. S. N. LEA, W. A. HALLETT, A. J. VARNEY, C. T. CHANTLER, P. E. G. BAIRD, J. D. SILVER, A. R. LEE, J. BILLOWES, Intra-cavity laser resonance spectroscopy of hydrogen-like silicon ions, Phys. Lett. A185 (1994) 327-332.
30. E. TAKACS, E. S. MEYER, J. D. GILLASPY, J. R. ROBERTS, C. T. CHANTLER, L. T. HUDSON, R. D. DESLATTES, C. M. BROWN, J. M. LAMING, U. FELDMAN, J. DUBAU, M. K. INAL, Polarization measurements on a magnetic quadrupole line in Ne-like barium, Phys. Rev. A54 (1996) 1342-1350. [first absolute polarization studies performed on an EBIT] 40. C.T. Chantler, D. Paterson, L.T. Hudson, F.G. Serpa, J.D. Gillaspy, E. Takacs, "Absolute measurement of the resonance lines in heliumlike vanadium on an electron-beam ion trap," Phys. Rev. A62 (2000) 042501:1-13
Investigation of new structure in atomic systems has continually developed our understanding of physics and quantum phenomena. One of the goals of much current research is to test Quantum Electro-Dynamics (QED) critically in new and important regimes. Some areas of parallel investigations include exotic atoms like muonic hydrogen, muonium, and positronium, and some investigations have involved g-2 experiments in different systems. Most effort has been directed to Lamb shift measurements in hydrogenic and helium-like systems. A significant realisation of recent years is that these complementary endeavours are investigating different fundamental issues and making major contributions to different fields.
Here the atomic scattering factor is given for Uranium at medium X-ray energies (keV). Click the figure for the corresponding attenuation coefficients.
How can relativistic quantum mechanics predict absorption and scattering coefficients, and are the results accurate?
Some of our theoretical developments in the computation of form factors have resulted in significant improvements upon earlier work, which can be tested by suitable experiments. The computations have been confirmed in selected regions. Atomic form factors determine photoelectric cross-sections, elastic and inelastic scattering cross-sections and X-ray (Bragg-Laue) coherent diffraction profiles. Major discrepancies exist between theory and experiment. The Web database has been receiving 20000 hits per month since itÕs electronic installation as one of the three major references for atomic form factors and attenuation coefficients. Reliable knowledge of these factors is required for conventional fields such as crystallography and radiography, and also for the new fields of X-ray Anomalous Fine Structure (XAFS) and Multiple-wavelength Anomalous Dispersion (MAD).
See
26. C. T. CHANTLER, Theoretical form factor, attenuation and scattering tabulation for Z=1-92 from E=1-10 eV to E=0.4-1.0 MeV, J. Phys. Chem. Ref. Data 24 (1995), 71-643.
39. C. T. CHANTLER, Detailed new tabulation of atomic form factors and attenuation coefficients in the near-edge soft X-ray regime (Z=30-36, Z=60-89, E=0.1 keV 8 keV), addressing convergence issues of earlier work, J. Phys. Chem. Ref. Data. 29(4) (2000) 597-1056.
Our recent experiments are two orders of magnitude more accurate than earlier work and reveal new physics, new processes and new applications. If we understand how light interacts with matter, we can use this insight in further applications.
The way that X-rays interact with matter should be well understood. However, deviations between latest theoretical computations lies at the 10% level over much of the energy ranges, for most elements. Even for the most investigated elements such as Si, Cu, Ag, Au, the few experiments which claim 1% precision show variation of 5-30%. We are addressing this with synchrotron experiments and with state-of-the-art facilities. Recent results have broken through this barrier to an unprecedented 0.01% precision and 0.02%-0.3% accuracy - an improvement of two orders of magnitude over previous work.
See
2. C. T. Chantler, "Towards improved form factor tables", pp 61-78, Invited review chapter in Resonant Anomalous X-Ray Scattering. Theory and Applications, G. Materlik, K. Fischer, C.J. Sparks, eds, (Elsevier, North-Holland, 1994).
See
X-ray Absorption Fine Structure (XAFS) is a complex structure seen in the absorption coefficient just above the absorption edge, where an incoming X-ray has enough energy to ionise an electron from a particular bound state. The oscillations seen are particularly due to an interference effect between the emitted photoelectron and its own reflected wave. This signature allows many investigations of local structural information for crystallographers, chemists, medical scientists and mining / engineering investigations.
Some third or more of Australian synchrotron research uses XAFS (and the related technique called XANES) to indentify band distances, chemical valence, nearest neighbour coordination and geometry, and local structure.
Our new experimental techniques allow XAFS determination with an accuracy increased by up to two orders of magnitude, which in turn challenges all available theory and modelling. Our analytical work puts these discrepancies on a firm foundation, and our theoretical development holds promise to develop new tools and methods of insightful analysis.
With Joel Brugger, Chris Ryan, Don MacNaughton and others, we received a large LIEF grant to develop these resources for high-accuracy experiments and extreme chemistry and earth science investigations.
See
71. C. WITTE, C.T. CHANTLER, E.C. COSGRIFF, C.Q. TRAN, Atomic cluster calculation of the X-ray near-edge absorption of copper, Radiation Physics & Chemistry 75 (2006) 1582-1585 [Proof of concept for the Finite Difference Method for XANES in copper]
77. J. D. BOURKE, C. T. CHANTLER, C. WITTE, Finite Difference Method Calculations of X-ray Absorption Fine Structure for Copper, Physics Letters A, 360 (2007), 702-706 [First demonstration that Finite Difference Method theory can be applied successfully in the XAFS regime.]
The experimental measurements and high accuracy have a long history enmeshed with developments of synchrotron diagnostics and calibration systems. Selected highlights follow:
43. C. T. CHANTLER, C. Q. TRAN, D. PATERSON, Z. BARNEA, D. J. COOKSON, Direct Observation of Scattering Contribution in X-ray Attenuation
Measurement, and evidence for Rayleigh scattering from copper samples rather than thermal-diffuse or Bragg-Laue scattering, Rad. Phys. Chem. 61 (2001) 347-350.
82. J. L. GLOVER, C. T. CHANTLER,
The Analysis of X-ray Absorption Fine Structure: Beam-line independent interpretation,
Meas. Sci. Tech. 18 (2007) 2916-2920 [How XERT resolves major anomalies in current research.]
This is a new field which we are beginning to explore. The first-fruits are:
Another new field, because both theory and experiment are largely intractable for low energy electrons.
Our experimental and theoretical approaches show great promise:
Powder Diffraction is often required for structural determination of biologically
active molecules, viruses, proteins or enzymes as well as for small inorganic molecules, especially
where the samples cannot be grown into large crystals. Standards for powder diffraction are well-known and widely used; though not frequently used
in local Australian research. These standards are dominated by pure silicon powder and lanthanum hexaboride
powder, which are the two principal lattice (and intensity) standards used in the world today.
These standards are maintained by NIST. They determine the lattice parameter of
an unknown sample under investigation and are a critical tool in determining
the synchrotron beam energy in an experiment.
Additionally, they monitor and can reveal several types of systematic errors in typical experiments. In recent work using the X-ray Extended Range Technique (XERT) we have redetermined the
lattice spacing of the second standard (LaB6) compared to the primary standard (Si) and find several
standard deviations of discrepancy. This (i) proves that synchrotron techniques can be used to determine
such standards and (ii) is the most accurate determination of lattice spacing except for that of silicon
itself. This opens up the way for the implementation of new standards and methods of analysis. See
73. N. A. RAE, C. T. CHANTLER, C. Q. TRAN, Z. BARNEA,
High-Precision Energy Determination of Synchrotron Radiation From Powder
Diffraction and Investigation of Profile Widths,
Radiation Physics & Chemistry 75 (2006) 2063-2066 [New technique for energy calibration.]
79. C. T. CHANTLER, N. A. RAE, C. Q. TRAN, Accurate determination and correction of the lattice parameter of LaB6 (standard
reference material 660) relative to that of Si (640b), J. Appl. Cryst. 40 (2007) 232-240 [New technique for powder diffraction standards.]
These issues impact upon X-ray diffraction theory. My diffraction theory
is the first dynamical theory for non-ideally imperfect curved crystals
(and simpler subclasses) and shows significantly greater agreement for
perfect curved crystal profiles than previous work. The X-ray interaction with photographic emulsions is an interesting application of
ideas from basic physics.
Active areas of interest and development include ion chamber
optimisation, new detector technology, state-of-the-art spectrometry
and 2-dimensional (backgammon) proportional counters. Applications of these ideas have led to new calibration devices for
radiography and mammography, now patented in the US as part of the Quantum
Metrology Group effort in the Atomic Physics Division
at the National Institute for Standards and Technology, USA. See
29. C. T. CHANTLER, R. D. DESLATTES, A. HENINS, L. T. HUDSON, Flat and Curved Crystal Spectrography for Mammographic X-ray Sources, British J. Radiology, 69 (1996) 636-649.
31. L. T. HUDSON, R. D. DESLATTES, A. HENINS, C. T. CHANTLER, E. G. KESSLER, J. E. SCHWEPPE, Curved Crystal Spectrometer for Energy Calibration and Spectral Characterization of
Mammographic X-ray Sources, Medical Physics 23 (1996) 1659-1670.
Non-destructive Measurement of Nanoroughness:
Measurement and Theory of the Inelastic Mean Free Path of the Electron:
Powder Diffraction, X-ray Diffraction and X-ray Crystallography:
Applications to Chemistry, Earth Sciences, Biology and Organometallics:
Last modified: November 2011
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