NEW EXPERIMENTAL-METHOD FOR STUDYING ROTATIONALLY STATE-SELECTED ION-MOLECULE REACTIONS

A new apparatus is described in which a beam of molecular ions in a selected vibration-rotation state is prepared by field ionization of high Rydberg states, in an adaptation of the zero-kinetic-energy photoelectron technique. The state-selected ions undergo low energy reactive collisions within a molecular beam and the ionic products are detected in a quadrupole mass filter. The Rydberg states are populated by two-color stepwise multiphoton excitation, and by tuning to the pseudocontinuum of high-Rydberg states associated with different vibration-rotation states of the ion core, different states of the ion are selected and the effect on reactivity determined. Some preliminary results for the H2+H2+→H 3+ reaction are reported. © 1994 American Institute of Physics.