We study two-photon excitation of Rydberg states of atoms under stimulated adiabatic passage with delayed laser pulses. We find that the combination of strong interaction between the atoms in Rydberg state and the spontaneous decay of the intermediate exited atomic state leads to the Rydberg excitation of precisely one atom within the atomic ensemble. The quantum Zeno effect offers a lucid interpretation of this result: the Rydberg blocked atoms repetitively scattering photons effectively monitor a randomly excited atom, which therefore remains in the Rydberg state. This system can be used for deterministic creation and, possibly, extraction of Rydberg atoms or ions one at a time. The sympathetic monitoring via decay of ancilla particles may find wider applications for state preparation and probing of interactions in dissipative many-body systems.
In order to investigate an interaction of an electromagnetic field with Rydberg atoms it is necessary to transfer atoms from ground state to Rydberg state with specified values of quantum numbers. The point is that for each chemical element the way of producing Rydberg atom atoms is strictly individual. In this paper Al atoms are transferred to Rydberg states by nF scheme using a system of lasers and frequency converters on nonlinear crystals. The Au atoms are brought to Rydberg state by three stages of laser excitation.
The history of Rydberg states in atoms and molecules will be briefly summarized. If the ground state of a molecular system is unstable (as for example two He atoms) while most excited states are stable Rydberg states, we may describe the system as a Rydberg molecule. The simplest diatomic example is the
He2 molecule, while the simplest polyatomic system would be the
H3 molecule discovered only in 1979. In recent years many other examples have been studied and will be briefly summarized.