Stark Rydberg states. Probing and manipulating the ion core

Rydberg states are highly susceptible to the perturbing effects of an applied electric field, and hence lend themselves to novel applications which form the subject for the investigations presented herein. The Stark spectra of autoionising n = 10-20, υ+ = 1 Rydberg states of NO, probed by two-colour excitation, via selected levels of the A 2Σ+ υ' 1 state for fields of 10-1000 V/cm have been investigated through a combination of experimental and theoretical techniques. Matrix diagonalisation and Multichannel Quantum Defect Theory simulations are presented, which show excellent agreement with the experimental results over a range of energies and fields. It is demonstrated that, using this bilateral approach, the Stark spectra can be used to gain greater insight into the complex electron - ion core interactions than can be achieved with zero-field spectra alone, through parametrisation in terms of quantum defects. Trajectory calculations for a beam of Rydberg atoms in the inhomogeneous electric field created by a dipole, quadrupole and hexapole are presented. These demonstrate that significant deflection and focusing of Rydberg atoms and molecules should be achievable under realistic experimental conditions. Controlled deflection of a beam of krypton atoms in the field of a dipole was realised experimentally. The observed deflection of up to 3 mm over an axial distance of 8 cm is in good agreement with the trajectory predictions, as is the variation of the deflection with selected quantum state. Finally an investigation into the possible control of the orientation of a dipolar ion core using Stark Rydberg states is presented. Matrix diagonalisation calculations are shown which suggest that significant orientation can be achieved, the degree and direction of which can be controlled by appropriate selection of the state excited and magnitude of the field applied. These novel investigations demonstrate the potential of Rydberg states in an electric field to both provide an insight into the nature of the ion core and to control its degrees of freedom. (author)