Collisional Effects on the Antiprotonic Helium Hyperfine Structure Measurement

We report preliminary results from a systematic study of the experimental conditions for a measurement of the hyperfine (HF) structure of antiprotonic helium (n,l) = (37,35). Improvements to the laser system have increased the peak-to-total signal and allowed the delay of the second laser to be extended. We have completed the first experimental measurements of the relaxation collision rate between HF states, by which antiprotonic helium atoms undergo inelastic spin exchange collisions. We show that a microwave induced p-pulse between HF states is achieved and that a higher signal-to-noise ratio than our previous results is possible. The study was carried out at the Antiproton Decelerator (AD) at CERN.