6533b7d9fe1ef96bd126cc78

RESEARCH PRODUCT

First Observation of Atomic Levels for the Element Fermium (Z=100)

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description

The atomic level structure of the element fermium was investigated for the first time using a sample of $2.7\ifmmode\times\else\texttimes\fi{}{10}^{10}$ atoms of the isotope $^{255}\mathrm{F}\mathrm{m}$ with a half-life of 20.1 h. The atoms were evaporated from a filament and stored in the argon buffer gas of an optical cell. Atomic levels were sought by the method of resonance ionization spectroscopy using an excimer-dye-laser combination. Two atomic levels were found at wave numbers $(25\text{ }099.8\ifmmode\pm\else\textpm\fi{}0.2)$ and $(25\text{ }111.8\ifmmode\pm\else\textpm\fi{}0.2)\text{ }\text{ }{\mathrm{c}\mathrm{m}}^{\ensuremath{-}1}$. Partial transition rates to the $5{f}^{12}7{s}^{2}$ $^{3}H_{6}^{e}$ ground state have been determined from their saturation characteristics. Multiconfiguration Dirac-Fock calculations suggest that the leading orders of these levels could be the $5{f}^{12}7s7p$ $^{5}I_{6}^{o}$ and $5{f}^{12}7s7p$ $^{5}G_{5}^{o}$ terms.