| Summary: | Ytterbium (Yb) atoms frozen in a solid neon (Ne) matrix qualitatively retain the structure of free atoms. Most of the Yb transitions are found to be blue-shifted in both absorption and emission spectra. Transitions also acquire significantly broadened linewidth, which can be a few nanometers for outer-shell transitions and as narrow as 0.03 nm (or 120 GHz) for inner-shell transitions. We explicitly demonstrate that the linewidth broadening is homogeneous for the 6s2 1S 0 - 6s6p 1 P1 transition. Splitting of transitions is observed as well, and is attributed to the broken spherical symmetry of the Yb trapping sites in solid Ne.
The lifetimes of 6s6p 3 P0,1 in both 171Yb and 172Yb are measured in solid Ne using the spectrally-resolved fluorescence-decay technique. The finite vacuum lifetime of 6s6p 3P0 in 171Yb is due to the hyperfine quenching, and gives the natural linewidth of the Yb clock transition. With the measurements in solid Ne, we extract this vacuum lifetime for the first time after correcting for various medium effects. One effect is the index-of-refraction dependence of the spontaneous emission, of which we perform an independent calibration based on the 6s6p 3P1 lifetime in vacuum and in solid Ne. We obtain a vacuum decay rate of (4.42+/-0.35) x10--2 s--1for 6s6p 3P0 in 171Yb, which agrees with a recent calculation.
The feasibility of optically polarizing 171Yb nuclei in solid Ne is discussed. The excitation rate of Yb transitions in solid Ne is suppressed by the same factor by which the absorption linewidth is broadened. The optical pumping efficiency for nuclear spins is estimated to be further suppressed by four orders of magnitude due to the presence of the crystal field.
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