Hydrogen molecules are excited in a molecular beam to Rydberg states around n=17-18 and are exposed to the inhomogeneous electric field of an electric dipole. The large dipole moment produced in the selected Stark eigenstates leads to strong forces on the H2 molecules in the inhomogeneous electric field. The trajectories of the molecules are monitored using ion-imaging and time of flight measurements. With the dipole rods mounted parallel to the beam direction, the high-field-seeking and low-field-seeking Stark states are deflected towards and away from the dipole, respectively. The magnitude of the deflection is measured as a function of the parabolic quantum number k and of the duration of the applied field. It is also shown that a large deflection is observed when populating the (17d2)1 state at zero field and switching the dipole field on after a delay. With the dipole mounted perpendicular to the beam direction, the molecules are either accelerated or decelerated as they move towards the dipole. The Rydberg states are found to survive for over 100 micros after the dipole field is switched off before being ionized at the detector and the time of flight is measured. A greater percentage change in kinetic energy is achieved by initial seeding of the beam in helium or neon followed by inhomogeneous field deceleration/acceleration. Molecular dynamics trajectory simulations are presented highlighting the extent to which the trajectories can be predicted based on the known Stark map. The spectroscopy of the populated states is discussed in detail and it is established that the N+=2, J=1, MJ=0 states populated here have a special stability with respect to decay by predissociation.

The Stark effect in autoionizing Rydberg states of NO, n=10–20,v+=1, is studied by a combination of experimental and theoretical methods. Double resonant excitation via selected intermediate rotation levels of the A 2Σ+, v′=1 state is carried out in the presence of fields 0–1000 V/cm. The spectra are simulated using both matrix diagonalization and full multichannel quantum defeat theory (MQDT) approaches, providing a test of quantum defect parameters and transition dipoles for Rydberg series from l=0 to l=4. The use of the same input parameters in these two types of calculation allows comparison of the validity and utility of these methods.

The controlled deflection of Rydberg atoms in an inhomogeneous electric field is demonstrated and shown to be in agreement with predictions based on a well-defined Stark map. Krypton atoms in a supersonic beam are excited in a two-colour multiphoton process to selected Stark states with n = 16-19 and undergo deflections in the field of an electrostatic dipole. The spatial distribution of the deflected atoms is monitored by ion imaging. The atoms travelling ~10 cm in the beam direction after excitation are deflected from the beam axis by distances of up to 3 mm, the interaction with the field taking place over 40 µs. Simulations of the trajectories agree well with the experimental results, demonstrating that the detected Rydberg atoms are those which have not undergone decay processes in the 40 µs applied field.

A novel theoretical study of the control of translational motion of atomic and molecular Rydberg states in inhomogeneous static electric fields is presented. Simulations have been carried out demonstrating that, under realistic conditions, the deflection and focusing of Rydberg atoms and molecules should be achievable. Advantage is taken of the high susceptibility of the Rydberg states to external electric fields, allowing the use of much smaller fields than would be necessary for ground state neutrals. The simulations presented are for trajectories of Rydberg states with n = 18-20 in the fields of an electric dipole, quadrupole and hexapole. A deflection of 7 mm is predicted for n = 18 Rydberg states travelling parallel to the dipole after 100 µs time of flight. In the hexapole n = 20 Rydberg states are refocused to a spot size of the order of the laser beam waist (10 µm) after 20 µs. It is demonstrated that the hexapole can also act as a cylindrical lens if its axis is perpendicular to the Rydberg beam direction. Spontaneous emission and black-body decay rates are also calculated, and their variation with the applied field is investigated. The potential applications of this work might include the use of focusing and deflection for controlled low-energy collisions of Rydberg molecules with surfaces.

A spectroscopic study of the Stark effect in the predissociating v þ ¼ 0 Rydberg states of nitric oxide, (n ¼ 13-16) is reported. The states are excited by two-colour excitation via the A 2 AE þ , v ¼ 0, N ¼ 0 state in the presence of a field in the range 0-1125 V cm À1 , and the excitation is observed by using (2 þ 1) REMPI detection of nitrogen ( 2 D) atoms formed by predissociation. The spectra recorded over a range of fields are compared with, and show excellent agreement with, multichannel quantum defect theory (MQDT) simulations of the absorption spectra applied in the bound state formalism of Sakimoto [J. Phys. B. 22, 2727[J. Phys. B. 22, (1989]. The spectroscopy demonstrates the possibility of producing N( 2 D) or O( 3 P) atoms with very narrow centre-of-mass frame speed distributions and arbitrarily selected speed.