Yttrium in the peculiar A and B stars

UV plates covering the spectral interval from roughly 3700 to 4150 A and blue plates covering the range from 4200 to 4650 A are analyzed for nine Hg-Mn stars, three cooler Ap stars of the magnetic and spectrum-variable types, three Am stars, and three normal late A or B stars with effective temperatures of 7200 to 13,400 K. Lines of Fe I, Fe II, Sr I, Sr II, Y II, and Zr II are measured and identified on intensity tracings. Optimal model-atmosphere parameters are obtained, and abundances are calculated for Fe, Sr, Y, and Zr. It is found that Fe exhibits no order-of-magnitude excess or deficiency (relative to the solar value) in any star, that the range of iron abundances is much broader for the Hg-Mn stars than for the other types, and that Sr, Y, and Zn are greatly enhanced in the Hg-Mn stars. An attempt is made to determine how the observed Sr, Y, Zr abundance pattern might result from s-process and r-process nucleosynthesis.