Isotope shift of the electric-dipole transition in Os−

Abstract

The isotope shift of the bound-bound electric dipole transition at 1162.75 nm in the osmium anion was measured by high-precision collinear laser spectroscopy. The transition was observed in all naturally occurring isotopes, including ${}^{184}$Os${}^{\ensuremath{-}}$ with a natural abundance of 0.02$%$. We combined the data with our prior measurements of the hyperfine structure in ${}^{187}$Os${}^{\ensuremath{-}}$ and ${}^{189}$Os${}^{\ensuremath{-}}$ and used them to determine experimental values for the isotope shift coefficients. The normal mass shift, specific mass shift, and field shift coefficients were found to be ${M}_{\text{NMS}}=141.4$ GHz u, ${M}_{\text{SMS}}=2.4(12.6)$ THz u, and $F=16.2(9.9)$ GHz fm${}^{\ensuremath{-}2}$, respectively. Theoretical values for the ${M}_{\text{SMS}}$ and $F$ parameters were calculated based on a series of relativistic configuration interaction computations and a Fermi-like charge distribution and found to be in good agreement with the experimental values.