Laser spectroscopy of the 1001-nm ground-state transition in dysprosium

Abstract

We present a direct excitation of the presumably ultranarrow $1001-\mathrm{nm}$ ground-state transition in atomic dysprosium. By using resonance ionization spectroscopy with pulsed Ti:sapphire lasers at a hot cavity laser ion source, we were able to measure the isotopic shifts in the $1001-\mathrm{nm}$ line between all seven stable isotopes. Furthermore, we determined the upper level energy from the atomic transition frequency of the ${}^{164}\mathrm{Dy}$ isotope as $9991.004\left(1\right){\mathrm{cm}}^{-1}$ and confirm the level energy listed in the NIST database. Since a sufficiently narrow natural linewidth is an essential prerequisite for high-precision spectroscopic investigations for fundamental questions, we furthermore determined a lower limit of $2.9\left(1\right)\mu \mathrm{s}$ for the lifetime of the excited state.