Accurate spectroscopy of Sr atoms

Abstract

We report the frequency measurement with an accuracy in the 100 kHz range of several optical transitions of atomic Sr : ${}^1{S}_0{-}^3{P}_1$ at 689 nm, ${}^3{P}_1{-}^3{S}_1$ at 688 nm and ${}^3{P}_0{-}^3{S}_1$ at 679 nm. Measurements are performed with a frequency chain based on a femtosecond laser referenced to primary frequency standards. They allowed the indirect determination with a 70 kHz uncertainty of the frequency of the doubly forbidden $5s^2^1S_0- 5s5p^3P_0$ transition of ${}^{87}$Sr at 698 nm and in a second step its direct observation. Frequency measurements are performed for ${}^{88}$Sr and ${}^{87}$Sr, allowing the determination of ${}^3{P}_0$, ${}^3{P}_1$ and ${}^3{S}_1$ isotope shifts, as well as the ${}^3{S}_1$ hyperfine constants.

12 pages, 16 figures