EXPERIMENTAL STUDIES OF HIGH-LYING RYDBERG STATES IN ATOMIC RUBIDIUM

This paper summarizes a long series of experiments that have been done on Rydberg states of Rb. The basic experimental technique that has been used is atomic-beam laser spectroscopy which allows both low-resolution and high-resolution studies. Excitation of Rydberg states is provided by single-photon absorption from a suitably frequency-doubled rhodamine 6G tunable laser. Detection is done by field ionization and ion counting. These techniques have allowed us to study the critical ionizing field, which has been found to follow classical, hydrogenic behavior closely. Rydberg states of Rb have been observed from n=28 up to n>100. High-resolution spectroscopic studies have led to measurement of the fine structure for np levels located between n=28 and n=60, as well as the isotope shift of the ground state.