Tandem time-of-flight experiment for low energy collision studies

We present an experiment adapted to collisional studies of cluster ions bas ed on a laser vaporization setup coupled to a supersonic expansion. The ion s are selected in a first time-of-flight, slowed down to the desired energy , and collided in an octopolar guide. The parent and fragment ions are then reaccelerated in order to be mass analyzed in a reflectron time-of-flight. An original method for the extraction of the ion that uses a double voltag e pulse, is proposed. The experiment has been applied to collisions of hydr ated cobalt ions. An absolute cross section of 17 Angstrom(2) for the loss of one water molecule by Co(H2O)(2)(+) in collision with neon at a center-o f-mass energy of 10 eV,has been determined, with an accuracy of 10%. The th reshold for this reaction has been measured at 1.5 eV and is in good agreem ent with the existing Literature (Dalleska et al. J. Am. Chem. Sec. 1994, 1 16, 3519). Ions that cannot be formed by conventional ligand exchange metho ds, can also be studied. As an example, the threshold for dehydration of th e Co-2(H2O)(+) ion has been measured at 1.5 +/- 0.2 eV. (C) 2000 American S ociety for Mass Spectrometry.