Comment on “Laser cooling of Yb173 for isotope separation and precision hyperfine spectroscopy”

Abstract

We present measurements of the hyperfine splitting in the Yb-173 6s6p 1 P o 1 (F = 3/2, 7/2) states that disagree significantly with those measured previously by Das and Natarajan [Phys. Rev. A 76, 062505 (2007)]. We point out inconsistencies in their measurements and suggest that their error is due to optical pumping and improper determination of the atomic line center. Our measurements are made using an optical frequency comb. We use an optical pumping scheme to improve the signal-to-background ratio for the F = 3/2 component.

Absolute frequency measurements of the ${}^1{\rm S}_0 \rightarrow {}^1{\rm P}_1$ transition in ytterbium

“…For odd isotopes, quantum interferences and polarization effects (16 , 23 ) can also lead to sub-MHz shifts of the resonances. In the particular case of the F = 5/2 → F = 3/2 hyperfine transition in 173 Yb, very specific polarizations of the laser with respect to the residual magnetic field would result in an optical pumping effect (24 ) and forbid detection of fluorescence for this transition. We do not claim in this work to measure separately transition frequencies for 172 Yb and 173 Yb F =5/2→F =3/2 , and the presence or the absence of the 173 Yb F =5/2→F =3/2 peak in the fluorescence spectrum can only induce sub-MHz level uncertainty on the common measurement largely dominated by the 172 Yb transition frequency value.…”