Data Interchange

A single XAS spectrum is a very useful unit of currency for a number of reasons:

• We send data to and receive data from our collaborators
• We publish individual spectra in journal articles
• We extract XAS spectra from large, complex, multi-spectral data sets
• We write web-based and desktop applications (for instance, a standards database) that traffic in single spectra
• We write data analysis software that needs to reliably import data that comes from many sources.

Conventional XAS

1. In a conventional XAS experiment, we measure a sample somewhere between 2 and 10,000 scans, possibly requiring dead-time or other corrections
2. Some data processing happens to correct, calibrate, and/or align the data
3. Those scans are then merged into a single spectrum that becomes our unit of currency

A data interchange standard is about how we express the merged spectrum (i.e. the blue one).

Fancy experiments XAS

Imaging experiments

In an imaging experiments the heterogeneity of our samples is measured. XAS can be measured on particular spots.

Tappero et al, New Phytologist 175:4, 641-654, (2007) doi:10.1111/j.1469-8137.2007.02134.x

Difraction anomalous fine structure (DAFS)

An anomalous scattering experiments yields energy-dependent scattering intensities. These are converted into χ(k) spectra and interpreted as position selective EXAFS.

Ravel et al. PRB 60, 778-785 (1999) doi:10.1103/PhysRevB.60.778

Non-resonant inelastic scattering

A NIXS experiment can used to measure a XANES spectrum in an X-ray energy loss channel.

Bergmann, et al. Chem. Phys. Lett. 369 184 (2003) doi:10.1016/S0009-2614(02)02003-1