Abstract.We have observed "dark resonances" in the A-type level structure, :formed by the 4S1/2 ground state, the 4P1/2 excited state and the low lying metastable 3D3/2 state in the Calcium ion, confined in a Paul radio-frequency trap. These Doppler-free and potentially very narrow resonances were used to determine the magnetic dipole hyperfine interaction constant A for the 4P1/2 and 3D3/2 state of 43Ca+, giving -142(8) MHz and -48.3(1.6) MHz, respectively. From measurements of the P-D (El) and S-D (E2) transition wavelength in a mixture of 43Ca + and 4°Ca + we determined the isotope shifts of these lines.

Abstract. The lit~times of both metastable 3D-levels of Ca + have been measured using the ion storage technique. Operation at UHV-conditions eliminated the earlier reported problems of collisional finestructure mixing between those states [1], which is inherent to measurements at buffergas background. The results of "c(D3/2) = ] 113(45) ms and x(Ds/2)= 1054(61) ms improve our earlier result [1] by almost one order of magnitude and are in good agreement with recent theoretical calculations [3,4,5].

Abstract.We have performed a laser microwave double resonance experiment on 43Ca+ ions stored in a Paul ion trap. The ground state hfs splitting has been determined to A v = 3 225 608286. 4(3)Hz. The value is corrected for small Zeeman, Stark and second order Doppler shifts as well as for light shift effects caused by the laserfields. The uncertainty is mainly determined by the errors of these corrections.

Abstract. The lifetime of the metastable 3 D3/2 and 3 Ds/2 states of Ca + ions is determined in a r.f. ion trap by laser excitation of this levels and subsequent time delayed probing of the state population by a second laser. In a buffer gas atmosphere of about 1 0 -s -1 0 -6 mbar of He we observe quenching to the ground state and strong finestructure mixing of the two D-states. This mixing allowes only the determination of the combined lifetime. Our result of z(3D)= 1.24 (39) s is in good agreement with theoretical calculations.

Ca + ions confined as a cloud in a Paul trap were excited and cooled by radiation from two lasers, tuned to the 4s 2 S 1/2 -4p 2 P 1/2 and 4p 2 P 1/2 -3d 2 D 3/2 transitions. The strong fluorescence of these lines disappears when we excite the ions simultaneously by a third laser on the 3d 2 D 3/2 -4p 2 P 3/2 line because of population trapping in the metastable 3d 2 D 5/2 state, into which the 4p 2 P 3/2 level decays. From the time dependence of the fluorescence after blocking the third laser we determined the lifetime of the 3d 2 D 5/2 level. Our result of τ = 1064(17) ms improves earlier results and agrees with the value recently computed by Liaw using the Brueckner approximation.