Measurement of the hyperfine structure of the S1/2-D5/2 transition in 43Ca+

The hyperfine structure of the 4s S-2(1/2)-3d S-2(5/2) quadrupole transition at 729 nm in Ca-43(+) has been investigated by laser spectroscopy using a single trapped Ca-43(+) ion. We determine the hyperfine structure constants of the metastable level as A(D5/2)=3.8931(2) MHz and B-D5/2=4.241(4) MHz. The isotope shift of the transition with respect to Ca-40(+) was measured to be Delta(43,40)(iso)=4134.713(5) MHz. We demonstrate the existence of transitions that become independent of the first-order Zeeman shift at nonzero low magnetic fields. These transitions might be better suited for building a frequency standard than the well-known "clock transitions" between m=0 levels at zero magnetic field.