At this website, the National Institute of Standards and Technology (NIST) offers the new Atomic Spectra Database Version 3.0, which "contains critically evaluated NIST data for radiative transitions and energy levels in atoms and atomic ions." Researchers can view the data by wavelengths or energy levels. Individuals can find articles summarizing the data and explaining the ground levels and...

This latest version of the Atomic Line List, hosted by the Department of Physics and Astronomy at the University of Kentucky and maintained by Peter van Hoof of the Canadian Institute for Theoretical Astrophysics, provides "a compilation of approximately 923,000 allowed, inter-combination and forbidden atomic transitions." The database allows users to identify observed atomic absorption and...