ATOMIC DATA FOR INTERPRETING STELLAR SPECTRA - ISOTOPIC AND HYPERFINEDATA

The quality of solar, stellar, and interstellar observations is now so high that we can see physical effects that have been assumed to be in significant. In natural isotopic mixtures essentially all atomic lines are asymmetric because of isotopic and hyperfine components. In astro physics the effects of isotopic components have been generally ignored in the case of Ti, Cr, Fe and Ni. Ignoring isotopic splitting introdu ces the following systematic errors: (1) the use of bisectors to deter mine velocity fields is incorrect; (2) Fourier analysis of line profil es to determine rotational, microturbulent, and macroturbulent velocit ies is incorrect; and (3) damping constants are overestimated. When th e stronger components become saturated, the weak components are still on the linear part of the curve of growth. This introduces the additio nal systematic errors; (4) wavelengths of saturated lines are shifted; and (5) abundances determined from equivalent widths are wrong. In ad dition the Doppler width and Voigt profile of each isotope are signifi cantly different. It is imperative that laboratory measurements be mad e to determine the isotopic splitting of every energy level of every s table isotope of every atom and ion as is now routinely done for actin ides and for diatomic molecules. Hyperfine splitting should be measure d as well for those isotopes with nuclear spin. Russia, the United Sta tes, and other countries should stockpile pure stable isotopes so they will be available for these measurements. Computer programs for analy zing spectra including the hyperfine and isotopic splitting already ex ist. We now need the laboratory data.