Study of ''rare'' Rydberg states in a fast beam by resonant excitation Stark ionization spectroscopy

Weakly populated Rydberg states in a fast beam may be efficiently and selectively detected by resonant excitation to a higher Rydberg state which is subsequently Stark ionized. Since the laser excitation is Doppler-free, and therefore may resolve the Rydberg fine structure, the specific Rydberg state (or states) participating in the transition may be controlled through the laser frequency. This leads to the further possibility of microwave/laser double resonance experiments. Application of these techniques to the study of high-L Rydberg states of helium and H2 illustrate their potential. (author)