High-precision Microwave Spectroscopy of Quantum Defects in Rydberg States of Au and Al Atoms

We propose to create an atomic-beam laser-microwave spectrometer for investigation of Au (gold) and Al (aluminum) atoms in highly excited (i.e. Rydberg) states and to measure the fine-structure quantum defects of these atoms with high precision. The Rydberg states will be populated through stepwise excitation by dye lasers or their harmonics. Following the last stage of photo excitation the atoms will be transferred to their nearest Rydberg-state neighbors by microwave resonance at millimeter and sub-millimeter wavelength, and then they will be detected by state-selective field ionization (SFI) with accurately characterized electric-field pulses or ramps. As the frequency of microwave sources are tuned through resonance, the transitions between energy levels of Rydberg sequences will be observed with high accuracy and resolution. Quantum defects of Au and Al atoms and fine structure splittings ofthe energy levels of these atoms in high-lying states just below the ionization limit will be obtained. These data will allow the accurate calculation of energies of a large number of never-before-detected energy levels, upon which methods for sensitive trace detection of Al and Au in laboratory and environmental settings can be based.