Abstract

I will present high-resolution isotope shift spectroscopy of five calcium isotopes using direct frequency-combdriven Raman transitions between the terahertz-spaced 3d ²D_3/2 and 3d ²D_5/2 levels. Fig.1.c) shows absolute frequency measurements on a single ⁴⁰Ca⁺ [1]. The achieved relative accuracy of 5.5×10⁻¹² is nearly a factor of five better than the previous best Raman spectroscopy [2], and is currently limited by the inaccuracy of our atomic clock reference. By performing similar measurements on ^42,44,46,48Ca⁺ ions, we determined the isotope shift of this transition with an accuracy of about 25 Hz. These measurements in combination with precise measurements of the 4s ²S_1/2 −3d ²D_5/2 transition are today’s best isotope shift measurements to our knowledge and allow for improved bounds on new physics beyond the standard model [3].

© 2019 IEEE