Atomic data review

Atomic data review

We’ve reviewed, compiled and synthesized the laboratory atomic data needed for precise studies of the metallic absorption lines typically seen in quasar spectra.

A decade ago, it was a remarkable fact that we could measure the transitions of metallic ions in quasar spectra more accurately than in the laboratory. Such is the amazing power of cosmological redshift: it stretches the wavelengths of these transitions from the far ultraviolet, where laboratory experiments are very difficult, all the way into the optical range where telescopes can make much easier work of measuring them.

We were keen to see this situation reversed because we wanted to measure the fundamental constants of Nature in distant galaxies via the absorption lines they imprint on background quasar spectra. Without knowing the laboratory wavelengths accurately, it would have been impossible to measure anything meaningful from our quasar spectra.

Over the past decade, many laboratory spectroscopists have carefully and laboriously measured and re-measured all the main transitions we’re interested in. This has allowed us to put it all together, combining measurements were possible and doing additional calculations of the isotopic and hyperfine structures of these transitions.

In the hope this compilation may be useful, and to make sure it was peer-reviewed, we have now published:

Murphy M.T., Berengut J.C.,
Laboratory atomic transition data for precise optical quasar absorption spectroscopy,
2014, Mon. Not. Roy. Astron. Soc., 438, 338, arXiv:1311.2949.

For quasar absorption practitioners and aficionados, the database of transition data is available through Research Data Australia, with the database itself hosted as a GitHub repository. This can and will be updated easily when new measurements or calculations emerge.

Want something new or see something wrong in the database? Raise an issue on the GitHub repository here.