Based on a new detection scheme, optical Ramsey fringes with a resolution of 4 kHz on the Mg 1S0‐3P1 intercombination line (λ=457 nm) have been detected using laser cooled and trapped atoms. Due to a pulsed excitation sequence, the signals are free from phase errors caused by the interacting laser fields and by the relativistic Doppler effect, resulting in an accuracy better than Δν/ν≊10−15. The influence of the electron shelving in the metastable 3P1 level on the trap dynamics is monitored on the fast and closed 1S0‐1P1 cooling transition (λ=285 nm). Simultaneously recorded Ramsey fringes on a thermal atomic beam allow a direct measurement of the second order Doppler shift.
Time-resolved collinear fast-beam laser spectroscopy has been used to measure the lifetime of the T=23 537 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, J=9/2 odd-parity [abbreviated as (23 537)${\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}_{9/2}$] level in Nd ii. Nanosecond pulsed excitation was achieved with the Doppler switching technique. The fast ions were selectively excited from the metastable 4${\mathit{f}}^{4}$5d
6K9/2 level to the (23 537)${\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}_{9/2}$ level by the light of a cw dye laser. The decay of the resonance fluorescence photons emitted in the transition to the ground 4${\mathit{f}}^{4}$6s
6I7/2 level, as a function of the flight distance, was observed. The decay length was scaled into the decay time by the ion velocity, which was determined using the optical resonance itself. The lifetime is 27.7(9) ns.