534 Examples of Ultrafast Processes in Matter
two classical turning points. It is a radial wave packet, because only a few angular
momentum eigenstates can be excited (selection rule l → l ±1), and the angular
coordinates of the Rydberg electron are delocalized in a quantum mechanical
sense [10]. Each of these orbits correspond to approximately the same energy,
hence the same classical period. Therefore, with all particles moving in phase
along the various elliptical orbits, they arrive at the same time close to the nucleus,
as illustrated in Fig. 11.1. To the motion of the charged particle is associated an
electric current J = ev proportional to its velocity v. The Rydberg wave packet
is excited by a pump pulse. The energy absorbed by a delayed