Rate constants for the reactions of Kr+(2P3/2) with HCl and DCl and of Ar+ with HCl have been measured as a function of reactant ion/reactant neutral average center-of-mass kinetic energy (〈KEc.m.〉 ) at several temperatures. The measurements were made using helium as the carrier gas. From these data we have derived the dependences of the rate constants on the rotational temperature of H(D)Cl. Rate constants for the reaction of Kr+(2P1/2) with HCl have also been measured as a function of temperature. The rate constants for all of the reactions were found to decrease with increasing temperature. The rate constants were also found to decrease with increasing 〈KEc.m.〉 at low 〈KEc.m.〉 but then to increase at higher 〈KEc.m.〉 . A significant rotational temperature dependence of the rate constant was derived for the reaction of Kr+(2P3/2) with H(D)Cl. The analogous derivation for Ar+ reacting with HCl showed the rate constant for this reaction to be independent of the rotational temperature of HCl within experimental uncertainty.

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We report here the first measurements of rate constants involving cluster ions with more than five ligands. We have measured rate constants, or lower limits to rate constants, for the reactions of H+(H2O)n=2–11 with NH3, CH3CN, CH3OH, CH3COCH3, and C5H5N (pyridine). The experimental techniques needed to study these ions and neutrals at low temperatures are described. The reactions all proceed rapidly by proton transfer with varying degrees of ligand transfer. At low temperatures the rate constants are larger than the collision rate constant based on an ion–dipole potential. Reasons for this are examined. Thermal dissociation appears to control the size distribution of the primary ion clusters and to affect the observed product distribution.

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