The atomic cloud is cooled and pushed upwards by a counter-propagating lasers in an optical molasses configuration.
[2] In broad strokes, the Ramsey method involves exposing a cloud of atoms to a brief radiofrequency (rf) electromagnetic field; waiting a time T; briefly exposing the cloud to the rf field again; and then measuring what fraction of the atoms in the cloud have been driven from the initial state to final state.
[2] The microwave frequency is swept across the atomic transition over many repeated measurements.
[3] The precision of the Ramsey method is inversely proportional to the wait time T of the cloud.
[5] The idea of the atomic fountain was first proposed in the 1950s by Jerrold Zacharias.