The possibility of using neutral and double ionized erbium for atomic clocks of high precision is investigated. In both cases the narrow electric quadrupole clock transition between the ground and first exited states of the same configuration lies in optical region. The estimated ratio of decay width to transition energy is less then ${10}^{-20}$. We demonstrate that these transitions are not sensitive to blackbody radiation, and if other perturbations are also considered the relative accuracy of the clocks can probably reach the level of ${10}^{-18}$ or better.

• Received 25 June 2013

DOI:https://doi.org/10.1103/PhysRevA.88.032509