Cold reactive collisions between laser-cooled ions and velocity-selected neutral molecules

We report a new experimental method to study reactive ion-molecule collisions at very low temperatures. A source of laser-cooled ions in a linear Paul trap has been combined with a quadrupole-guide velocity selector to investigate the reaction of Ca(+) with CH(3)F at collision energies (E) over bar (coll)/k(B)>= 1 K with single-particle sensitivity. The technique represents a general approach to study reactive collisions between ions and polar molecules over a wide temperature range down to the cold regime.