Cowan Code: 50 Years of Growing Impact on Atomic Physics

Abstract

The famous Cowan’s book, “The Theory of Atomic Structure and Spectra”, published in 1981, and his suite of computer codes based on it, continue to be highly influential in atomic physics and many other research areas. As of September 2018, there have been more than 5000 citations to Cowan’s book and codes, and each year adds about 150 citations to this list. The present work briefly describes what these codes do and why they are responsible for most of the current progress in the analyses of atomic spectra. Various modifications of these codes, including my own, will also be described.

Calcium and Potassium Spectra in the EUV

“…Several K XI lines have been identified [54] with the aid of semi-empirically adjusted Hartree-Fock Relativistic (HFR) computations. The HFR code is a derivative of the Cowan code [55]. The Cowan code employed is of limited accuracy as a predictive tool, but various parameters can be adjusted to match experimental data.…”

The Allure of High Total Angular Momentum Levels in Multiply-Excited Ions

“…Jupén et al used the Cowan code (see Reference [66,67]) for guidance, a nonrelativistic Hartree-Fock (HF) atomic structure code that permits the external scaling of the Slater parameters. While the code yields sometimes shockingly inaccurate transition wavelengths when used in the ab initio mode (wavelength uncertainties of 20% are common), the results are much closer to reality when the Slater parameters are subjected to "standard scaling" values.…”

Orthogonal Operators: Applications, Origin and Outlook

“…Why should one use orthogonal operators when a conventional Slater-Condon approach such as Cowan's code [6,7] is so easy-to-use as a universal tool? Cowan's code has been a blessing for the experimental atomic physicist for the last 50 years, and it will no doubt continue to be so for many years to come.…”