Simulating cold atomic hydrogen production in linear radiofrequency ion traps

We simulated the motion of BaH + molecular ions which are sympathetically cooled by laser-cooled Ba + ions in linear quadrupole and octupole radiofrequency (RF) ion traps. By varying the trap voltages, we studied the velocity distribution of hydrogen atoms that would be produced upon threshold photodissociation of the BaH + . We found that hydrogen with a kinetic energy below 30 mK × k B can be produced in both traps, making the scheme suitable for loading hybrid ion-atom traps such as those used to synthesize and trap antihydrogen or study ultracold atom-ion collisions. We discuss how the dynamics of RF traps could be exploited to produce hydrogen below this limit by either driving the photodissociation transition with a small laser beam aligned along the axis of the trap, or by pulsing the laser during the micromotion turning points.