What are good, reliable databases of atomic spectra? I am looking for a database of atomic spectra, which contains


*

*atomic levels and their energies, electronic configurations, angular-momentum characteristics and lifetimes, and

*atomic transitions and their energies, initial and final states, linewidths and branching ratios,


and that kind of data, ideally for a broad range of neutral atoms and ions covering the full periodic table.
Ideally, I'm looking for reliable databases which do not have intermittent service interruptions, though databases from countries with intermittent service are also OK.
 A: I am sure that this won't cover everything you need, but a "competitor" to the NIST database that is used a lot in astrophysics is the Vienna Atomic Line Database VALD database of information on atomic and molecular transitions.
As I say, I think you will only get a subset of what you need here because it is focused on the data required to predict the emergent spectrum from a stellar atmosphere.
There are several mirror sites in different countries!
A: The gold standard for this is the NIST Atomic Spectra Database, which curates comprehensive lists of

*

*energy levels, together with their energies, angular momenta (i.e. term symbols) and Landé $g$ factors, as well as indications of how well-described they are by Hartree-Fock single-determinant approximations;

*transitions between levels, including their transition probabilities (connected to oscillator strengths and branching ratios);

*ground states and ionization energies; and

*Laser-Induced Breakdown Spectroscopy (LIBS) data,

for both neutral and ionized atoms. The data are predominantly of experimental origin and they are extremely well referenced; where good theory is available, it is also referenced.


(The only caveat is that the ASD's availability can be impacted by shutdowns of the US federal government; hence the need for alternatives.)

