How should we teach XAFS to undergraduate students?

Graduate and undergraduate education in chemistry, materials science, physics, chemical engineering and other disciplines often has a high emphasis on spectroscopies and other advanced diagnostic methods. To name only some of the most obvious examples, each of NMR, EPR, Raman scattering, IR spectroscopy, x-ray diffraction, thermogravimetric analysis and electrochemical characterization appear in varying degrees in the standard curriculum for these majors. At the undergraduate level, there is often an emphasis on phenomenology and practical application, rather than the most advanced theoretical treatments.

With only very rare exceptions, x-ray absorption fine structure (XAFS) and x-ray emission spectroscopy (XES) are not parts of the standard undergraduate or graduate educational curriculum even in specialties where XAFS makes frequent scientific contributions. The key point has always been access: why teach a technique that the typical student cannot use during the course and likely (from a statistical perspective) will never use? Basic education about XAFS instead falls to the distributed responsibility of individual research groups, beamline scientists and conference-based short courses or summer schools. If the students can't have hands-on experience in the way that they do with all of the above-mentioned, more common spectroscopies, then instructors of undergraduate spectroscopy courses make the pragmatic choice to omit the method.

Recently, however, new instrument design paradigms and the use of modern components by several research groups are leading to a nascent renaissance in laboratory (non-synchrotron) XAFS and XES. I've previously discussed the case for analytical XAFS, the similarities and differences between the different manifestations of x-ray fluorescence analysis and XES, and the unexpectedly high count rates of laboratory XES. Here, the question addressed is more forward-looking.

A growing number of research labs have or will build or purchase 'routine' laboratory XAFS and/or XES capability. By 'routine', I omit very advanced laboratory-based approaches such as those using high-harmonic generation to perform synchrotron-style time-resolved studies. Again, see the preceding article on the case for laboratory XAFS.

However, once a lab XAFS spectrometer is available as part of a supported user facility, such as the CEI-XANES spectrometer at the University of Washington, the above reservations begin to break down. Students now have ready access for both education and also research. In this context, when XAFS is viewed as a (potential) routine analytical technique rather than a specialist rare opportunity, many questions about educational methods and goals then arise. For example:

• What are the key phenomenon and experimental signatures that constitute the core of XAFS applications?
• What level of theory, as opposed to pragmatic fingerprinting and general principle analysis (or 'analysis') is appropriate in a first introduction?
• As the assumption is that the students have access to a lab XAFS spectrometer, what demonstration studies should they be assigned to perform?
• What is the 'classic' scientific literature on XAFS that will be intellectually accessible to advanced undergraduate students?
• What are examples of accessible, 'modern classic' studies where XAFS has strongly addressed contemporary research problems?

These only touch on initial planning for instruction, and there are certainly both similarities and differences between a University-based curriculum and that of ongoing, highly successful XAFS short courses at conferences. The key point from my perspective, however, is that the clock is ticking. This summer, I'm going to have some students in an advanced undergraduate laboratory on condensed matter physics learn about XAFS and perform demonstration studies (using CEI-XANES and the lab-based spectrometers in my lab at the University of Washington), then write reports with a 'usual' amount of error analysis, etc. At the end of their two week period working on XAFS, what should they know? What should be the most important things that I want them to remember in future years?

If you have advice, or otherwise have opinions or input on the problems of XAFS instruction at the undergraduate level, please comment on the article or email/message to me. I'm curious to hear the opinion of the broader specialist community.

While it will be several years before any large fraction of research universities have laboratory XAFS or XES capability in their on-site shared x-ray facilities, I hope that this exercise will lead to ideas about how to broaden and enrich the community of XAS users. All comments appreciated.