XDI and NeXuS formats for XAS data

This document discusses concepts for storing and communicating X-ray Absorption Spectroscopy (XAS) Data, and builds on earlier work on the XAFS Data Interchange Format format to consider how to format and communicate multiple spectra and more complex raw datasets for XAS data. The rationale for this work is to be able to better format and communicate XAS data between scientists, in on-line databases, in supplemental material for journals, and for general dissemination of scientific data through FAIR DATA principles.

The goal of this presentation is to to give some proof-of-concept work and begin engagement in a thoughtful consideration of these topics. We would like to see the IXAS and IUCr XAFS commission discuss these topics (perhaps establishing a Working Group), and to make a community-led recommendation. If you are reading this and interested, please contact me.

For the discussion here, the acronym XAS will be used to include all variations on X-ray Absorption Spectroscopy (XAS, XAFS, EXAFS, HERFD XAS) that represent a single measurement of the X-ray mass-attenuation or absorption coefficient \(\mu(E)\), though some special considerations may be discussed for some types of measurements. Extending the work here to releated spectroscopies is certainly worth considering and discussing.

Q2XAFS 2023 presentation slides: https://millenia.cars.aps.anl.gov/nxxas/Presentation/Newville_Q2XAFS2023.pdf

• XDI: XAFS Data Interchange Format
  • Overview of the XDI format
  • Some limitations of XDI
• Multi-Spectra Data Formats
  • Zip file of XDI files
  • Sqlite
  • XML, JSON, etc
  • CIF
  • HDF5 and NeXuS
• XAS schema for NeXuS based on XDI
  • Worked example of XDI and NeXuS formatted XAS data
  • Discussion
• References