Isotope Displacement and Hyperfine Structure in the Arc Spectra of Chromium, Molybdenum and Tungsten

Abstract

Several of the stronger lines of Mo I and W I in the region 4000 to 6100A are found to possess Structure. The W I lines are separated into three components which are roughly equally spaced with an overall separation of 0.1 ${\mathrm{cm}}^{\ensuremath{-}1}$. This structure is attributed to an isotope displacement of the even isotopes. Some of the Mo I lines are resolved into two components, while others, though not resolved, are broad and nonsymmetrical. The two component lines, with separation of 0.05 ${\mathrm{cm}}^{\ensuremath{-}1}$, are interpreted as being due to spin splitting of the odd isotopes. The broad lines with a width of about 0.06 ${\mathrm{cm}}^{\ensuremath{-}1}$ are interpreted as being due to a small isotope displacement. There is some evidence that $I=\frac{1}{2}$ for the odd isotopes of both Mo and W. There is also evidence that the magnetic moments of these odd isotopes are not large. The isotope displacements in the spectra of several elements are compared and the direction of displacement is discussed.