Illustration: Courtesy of S. D. Hogan, Ch. Seiler, and F. Merkt from ETH Zurich
Simulations of phase-space distributions showing the velocity vs position of the molecular cloud of in the Rydberg state at different junctures of the deceleration and trapping process. When created by photoexcitation at position and time zero, the Rydberg molecules have a mean longitudinal velocity of . In about the molecules are decelerated over a longitudinal distance of only to zero mean velocity. At this position the molecules are then held in an electrostatic trap for about . At any juncture, the molecules can be field-ionized and detected. Apart from reflecting the inhomogeneity of the electric field applied, the distributions illustrate that the conservative Stark interaction does not increase phase-space density (the density of points in each of the subsequent distributions).