Using magneto-optical traps to measure ion-atom collision cross sections

I have used the trap loss method to measure ion-atom total scattering cross sections. I measured the cross section for H+ and H ₂+ incident upon magento-optically trapped 85 Rb atoms in the 52S_1/2 ground state and the 52P_3/2 excited state. In order to obtain ground state cross sections the trap must be off while the ion beam is on to allow the atoms to decay to the ground state. Operating the trap in a pulsed fashion introduces some concerns about using the trap population rate equation which is derived for continuous operation. These concerns are addressed and the validity of this approach is demonstrated. The total scattering cross section for H+ and H₂+ on 85Rb in the 52S_1/2 ground state was measured from 3 to 10 keV and it was found that at comparable velocities H+ and H₂+ have the same cross section. I also measured total scattering cross sections for H+ on Rb in the 5 2P_3/2 excited state at 7 keV. The excited state cross sections are slightly smaller than those for ground state targets. The trap loss method can be extended to measure cross sections for any process that results in atoms being removed from the trap.