Two-photon optical Ramsey spectroscopy of freely falling atoms

Investigations have been conducted regarding the Doppler-free two-photon optical Ramsey spectroscopy of cold neutral atoms falling freely because of gravity. Recently, laser-cooled atoms were confined for long periods either in a magnetic quadrupole trap or in the radiation field of six orthogonal laser beams. However, the atoms were then perturbed by strong electromagnetic trapping fields. In the present study, the use of the earth's gravitational field for slowing laser-cooled atoms further is explored, taking into account the observation of the projectiles for extended periods in free fall near the turning point of their parabolic trajectories. It is found that the considered technique can provide simple interference signals of ultrahigh resolution without perturbing the atoms with trapping fields.