Abundances of Elements in Stars and Nebulae (Spectral Line Strengths from Astrophysical Data)

摘要

An attempt is made to compile empirical log (gf lambda)'s for lines of metallic ions of FeII, FeIII, CrII, TiII, and MnII. Here f is the Landenburg f, or oscillator strength, g is the statistical weight of the lower level, and lambda is the wavelength of the line. The curve of growth relates the equivalent width of a spectral line to the number of atoms capable of absorbing it and to the f-value of the transition involved. If the electron pressure and temperature in the stellar atmosphere are known, relative log gf lambda's can be determined. Furthermore, if laboratory absolute gf's are available for a few of these lines, then relative gf lambda's can all be converted to absolute gf lambda's. The advantages and limitations of these 'astrophysical' gf's are described, and it is emphasized that in order to secure adequate line strength data, one must (a) secure good line-intensity data (b) interpret these with the aid of a model atmosphere, taking into account effects of the stratification in the atmosphere. The gf lambda-values herein tabulated may be useful in analyzing the spectra of incandescent gases in laboratory or experimental sources of unknown temperature and pressure. (Author)