We discuss high resolution spectroscopy experiments, currently being performed at our laboratories, on Rydberg atoms in crossed electric and magnetic fields in the context of the work carried out by Pierre Jacquinot and co-workers on Rydberg states of field-free atoms and atoms in external electric fields.
Although the hydrogen atom has naturally served as the basis for extensive theoretical studies of the physics of highly excited atoms in strong external fields, experiments with this fundamentally important species in magnetic fields have not been reported, except for the most recent ones carried out in our laboratory.1,2 We report new results of studies on the spectroscopy of the atom in static homogeneous magnetic fields of strength B ≲ 6 T at excitation energies from high Rydberg states (n ≳ 20) into the ionization region (E ≲ +30 cm−1).
In highly excited Rydberg atoms, the excited electron is in a large, loosely bound orbit. Hence, in contrast with the ground states, the Rydberg states are very sensitive to external electric field and can be ionized in rather weak fields. The low ionization threshold of Rydberg states results in effective state-specific detection by the selective field ionization technique. \t In this thesis, high-resolution spectroscopy of Rydberg states of Rubidium using millimeter wave transitions and selective field ionization has been used as a probe of external electric and magnetic fields. Laser cooling and trapping techniques in a magneto-optical trap (MOT) are employed to have a high density and narrow velocity distribution for the atomic sample. In this work the magnetic field inhomogeneity inherent in a MOT is minimized and the stray electric field present at the trap region is compensated in order to have resolved spectra. The Stark line broadening of the spectra obtained in this work may be used to determine the electric field distribution in an expanding ultra-cold neutral plasma.