Population trapping in excited Yb ions

Resonant laser excitation of Yb ions confined in an rf ion trap is found to result in perfect population trapping in the highly metastable ${}_{}{}^2{}_{}{}^{}\mathrm{F}_{7/2}^{}{}_{}{}^{}$ state. The lifetime of this level is measured to be greater than 8 days. Population and depopulation of this level under narrow- and broad-band laser excitation conditions is investigated and its potentiality for ultimate-resolution laser spectroscopy indicated.