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 H2 in the n=30 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 500 m/s. In about 10 μs the molecules are decelerated over a longitudinal distance of only 3 mm to zero mean velocity. At this position the molecules are then held in an electrostatic trap for about 50 μs. 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).