Update of atomic data for the first three spectra of actinium

The last comprehensive experimental study of actinium spectra (Ac I-III) was made by Meggers et al. (1957) [1]. This was a result of a comprehensive study that took several years of work and produced many tens of high resolution spectrograms recorded on photographic plates archived at the National Institute of Standards and Technology (NIST). Since then, only a few fragmentary observations were made using laser spectroscopy methods. Atomic theory also made very little progress in interpretation of these spectra. These new developments have recently been consolidated in the new actinium datasets of the NIST Atomic Spectroscopy Database (ASD). This presentation will summarize the findings that went into this update. One of them is an exceptionally good quality of the old measurements and analysis of Meggers et al. (1957).

[1] W. F. Meggers, M. Fred, and F. S. Tomkins, J. Res. Natl. Bur. Stand. (U.S.) 58, 297 (1957)