I have developed a new version of my model atmosphere program called ATLAS12. It recognizes more than 1000 species, each in up to 10 isotopic forms, including all ions of the elements up through Zn and the first 5 ions of heavier elements up through Es. The elemental abundances are treated as variable with depth. ATLAS12 has 6 input files of line data containing 58,000,000 atomic and molecular lines. For each line the wavelength, identification, lower energy level, gf, radiative, Stark, and van der Waals damping constants are packed into 16 bytes. At each wavelength point in a frequency integration the profiles of all the significant nearby lines are computed and summed. The program and line files will be distributed in the fall of 1992.
There are no significant differences at A0 between an opacity-sampled model computed with ATLAS12 and opacity-distribution-function model computed with ATLAS9. ATLAS12 allows arbitrary abundances but is slower. The new program can be used to produce improved models for Am and Ap stars that include the effects of millions of lines.