Fig. 2

Beam dispersion. a Phase space distribution of the particles in a molecular packet directly behind the source (left side) and some flight distance down stream (right side). Δ x is the width of the detection zone, Δ v _i the velocity range that would be probed without (i=1) and with (i=2) the dispersion of the packet during the flight from source to detection. b phase space distribution of a continuous beam with the same velocity spread as the pulse in panel a