Observation of a narrow inner-shell orbital transition in atomic erbium at 1299 nm
A. Patscheider, B. Yang, G. Natale, D. Petter, L. Chomaz, M. J. Mark, G. Hovhannesyan, M. Lepers, F. Ferlaino
Abstract
We report on the observation and coherent excitation of atoms on the narrow inner-shell orbital transition, connecting the erbium ground state $[\mathrm{Xe}]4{f}^{12}{(}^{3}{\text{H}}_{6})6{s}^{2}$ to the excited state $[\mathrm{Xe}]4{f}^{11}({{(}^{4}{\text{I}}_{15/2})}^{0})5d{(}^{5}{\text{D}}_{3/2})6{s}^{2}{(15/2,3/2)}_{7}^{0}$. This transition corresponds to a wavelength of 1299 nm and is optically closed. We perform high-resolution spectroscopy to extract the ${g}_{J}$ factor of the 1299-nm state and to determine the frequency shift for four bosonic isotopes. We further demonstrate coherent control of the atomic state and extract a lifetime of 178(19) ms, which corresponds to a linewidth of 0.9(1) Hz. The experimental findings are in good agreement with our semi-empirical model. In addition, we present theoretical calculations of the atomic polarizability, revealing several different magic-wavelength conditions. Finally, we make use of the vectorial polarizability and confirm a possible magic wavelength at 532 nm.