Using the numerical techniques that have been successful in elucidating the low-lying part of the level scheme of atoms in magnetic fields pertaining to white dwarf stars and neutron stars, we have computed the energies and wave functions of ``circular'' Rydberg states (i.e., with \ensuremath{\Vert}m\ensuremath{\Vert}=n-1) with \ensuremath{\Vert}m\ensuremath{\Vert}=24--35 for laboratory fields up to several tens of teslas. We can, therefore, follow a number of physical properties, such as transition frequencies and radiative decay times, of circular states as functions of the magnetic field strength and make predictions that should be verifiable experimentally.
Helium atoms have been prepared in the circular $|n=55,\ensuremath{\ell}=54,{m}_{\ensuremath{\ell}}=+54\ensuremath{\rangle}$ Rydberg state using the crossed electric and magnetic fields method. The atoms, initially traveling in pulsed supersonic beams, were photoexcited from the metastable
1s2s3S1 level to the outermost, ${m}_{\ensuremath{\ell}}=0$ Rydberg-Stark state with
n=55 in the presence of a strong electric field and weak perpendicular magnetic field. Following excitation, the electric field was adiabatically switched off causing the atoms to evolve into the circular state with ${m}_{\ensuremath{\ell}}=+54$ defined with respect to the magnetic-field quantization axis. The circular states were detected by ramped electric-field ionization along the magnetic-field axis. The dependence of the circular state production efficiency on the strength of the excitation electric field, and the electric-field switch-off time was studied, and microwave spectroscopy of the circular-to-circular $|55,54,+54\ensuremath{\rangle}\ensuremath{\rightarrow}|56,55,+55\ensuremath{\rangle}$ transition at $\ensuremath{\sim}38.5$ GHz was performed.
Circular Rydberg states with
n=70 have been prepared in helium using a modified version of the crossed-fields method. This approach to the preparation of high-
n circular Rydberg states overcomes limitations of the standard crossed-fields method which arise at this, and higher, values of
n. The experiments were performed with atoms traveling in pulsed supersonic beams that were initially laser photoexcited from the metastable
1s2s3S1 level to the
1s73s3S1 level by resonance-enhanced two-color two-photon excitation in a magnetic field of 16.154 G. These excited atoms were then polarized using a perpendicular electric field of 0.844 V/cm, and transferred by a pulse of microwave radiation to the state that, when adiabatically depolarized, evolves into the
n=70 circular state in zero electric field. The excited atoms were detected by state-selective electric field ionization. Each step of the circular state preparation process was validated by comparison with the calculated atomic energy-level structure in the perpendicular electric and magnetic fields used. Of the atoms initially excited to the
1s73s3S1 level, $\ensuremath{\sim}80%$ were transferred to the
n=70 circular state. At these high values of $n, \mathrm{\ensuremath{\Delta}}n=1$ circular-to-circular Rydberg state transitions occur at frequencies below 20 GHz. Consequently, atoms in these states, and the circular state preparation process presented here, are well suited to hybrid cavity QED experiments with Rydberg atoms and superconducting microwave circuits.
In this dissertation I investigate cold Rydberg atoms and molecules in which the angular-momentum character of the quantum states involved strongly influences their properties and dynamics. In the first part I focus on long-range diatomic Rydberg molecules formed by a rubidium D-state Rydberg atom and a second rubidium atom in its ground state. Spectroscopic measurements of molecular binding energies are presented showing the effect of the Rydberg atom size and fine-structure coupling on the molecular potentials. A theoretical model is introduced that takes into account all relevant angular-momentum couplings between the molecular constituents, successfully reproducing experimental observations. Calculations of adiabatic potentials and binding energies, molecular-state lifetimes, electric and magnetic dipole moments are also presented. In the second part, I describe the production and magnetic trapping of cold circular Rydberg atoms. The circular Rydberg atoms are generated out of a cold gas of rubidium using the crossed-fields method and magnetically trapped. The trapping force is employed to induce center-of-mass oscillations of the trapped atom sample. Trap parameters and observed oscillation frequencies are used to measure the magnetic moments of the circular Rydberg atoms. Trap losses and the atomic internal-state evolution in the 300 Kelvin thermal background are also investigated.
Using a kind of potential model wave function for alkali metal atoms, we nonperturbatively study the effect of fine structure on the Rydberg spectra of Cs atom in a strong magnetic field. Our numerical results reveal spectral structure dramatically different from the well-established Paschen-Back effect, and we argue that the fine structure of the Rydberg Cs atom cannot be neglected even in a magnetic field as strong as several teslas. We also give an error estimate of our results and a word on possible experimental verification. \textcopyright{} 1996 The American Physical Society.
Circular atoms, i.e., Rydberg atoms with maximum angular momentum, are semiclassical atoms of great interest for Rydberg constant metrology and QED tests. Following a suggestion by Delande and Gay, we have prepared circular atoms by a new method, involving the adiabatic switching of crossed electric and magnetic fields. The method, which is demonstrated for Rydberg states of lithium (principal quantum number
n=20to25, is applicable over a wide variety of experiment conditions.