OPTICAL RAMSEY SPECTROSCOPY ON LASER-TRAPPED AND THERMAL MG ATOMS

High-resolution spectroscopic measurements on the 457 nm Mg intercombi nation line are reported. Studies have been performed both on atoms co ntained in a magneto-optical trap and on atoms in a thermal beam. We p resent a detailed analysis of various factors influencing resolution a nd accuracy for both setups, including direct comparisons. With the tr apped cold atoms, a stability of 8.7 x 10(-13) within 20 s has been ac hieved together with an accuracy of 2 x 10(-15). The direct comparison shows the limited stability of the thermal beam apparatus for integra tion times larger than 300 s. For shorter times, the thermal beam setu p is at present more stable by a factor of three, mainly because of a better signal-to-noise ratio.