Microwave spectroscopy, with Stark ionization detection, is used on fast beams of laser-excited atoms, (1) to study high angular momentum states of helium in order to test relativistic and QED contributions to their structure, (2) to study such states in the H2+ ion, (3) to study such states in heavy atoms, 4 to measure the n=4 Lamb shift in H, and 5) to study collisional properties of these high angular momentum states.
