Measurement of the Electric Quadrupole Moment of the4d D5/22Level inSr+88

Abstract

The quadrupole moment of the $4d\text{ }^{2}D_{5/2}$ level in $^{88}\mathrm{S}\mathrm{r}^{+}$ has been measured to be $2.6(3)e{a}_{0}^{2}$, where ${a}_{0}$ is the Bohr radius and $e$ the elementary charge. A single laser-cooled strontium ion was confined in an end cap trap with a variable dc quadrupole potential, and measurements were made on the $5s\text{ }^{2}S_{1/2}$--$4d\text{ }^{2}D_{5/2}$ transition at 674 nm using a femtosecond optical frequency comb. This work shows that measurements of the unperturbed $^{88}\mathrm{S}\mathrm{r}^{+}$ transition frequency with sub-Hz uncertainty are possible and is important in understanding the reproducibility of ion trap optical frequency standards.