Extensive spectroscopic data for multiply ionized scandium: Sc III to Sc XXI

Abstract

Context. Spectroscopic data for scandium is sparse, while an extensive set is needed to introduce this element into stellar opacity calculations and, more importantly, into stellar models dealing with radiative diffusion. Aims. Our goal is to provide extensive energy levels and radiative transitions data for nineteen ionization stages of scandium relevant to stellar interiors, namely from Sciii to Scxxi. Methods. We used the FAC code. This code provides ab initio theoretical values for energy levels in jj-coupling and oscillator strengths of all permitted transitions. Detailed correspondences are established with compiled data from the National Institute of Standards and Technology (NIST) database, to locate as much as possible the observed levels and lines at their experimental values and to estimate the quality of our data. Comparison were also made with the spectroscopic data delivered by Kurucz. Results. The theoretical data retained in tables include 21 842 levels and more than two millions transtions. By comparison, the NIST compilation gives a total of 820 levels and 677 gf -values. The good agreement obtained when comparing the new data with those of the NIST compilation demonstrates their quality. This work on scandium shows that the FAC code is efficient in providing spectrocopic data that are unavailable from laboratory analyses but necessary for accurate simulations of stellar plasmas.