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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We describe two versions of a high temperature flowing afterglow apparatus. With a stainless steel flow tube wrapped with heating tape we have obtained data over the range 300-1300 K. In a version with a ceramic flow tube in a commercial furnace we have obtained data over the range 300-1600 K. The ceramic version is designed to take data up to 1800 K, but we have encountered experimental problems at the upper temperature range. The design modifications to a standard flowing afterglow needed to make measurements at elevated temperatures are described in detail, as are problems associated with operating at elevated temperatures. Samples of data are given.

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Articles you may be interested inEffect of collisional quenching on the measurement of ion species mix in neutral beam injectors Vibrational quenching rate constants have been measured for NO+ (v >0) ions with 15 neutral quenching molecules by the SIFDT -monitor ion technique. The temperature dependence of the quenching rate constants for the reactions ofthe neutrals N 2 , CO 2 , and CH 4 has been investigated from 208 to 450 K. The dependence of the CH 4 quenching rate constant on collision energy has been determined in the energy range 0.03-0.12 eV at 208 and 296 K. Also measured are rate constants for some of the reactions pertinent to the monitor ion technique.

Three‐body association rate coefficients have been measured as a function of temperature for the clustering of HCl to HSO4−(H2SO4)m(HNO3)n ions for m = 0–3 and n = 0 and 1. The temperature coefficients of these clustering reactions were found to increase with increasing cluster size in agreement with studies on other systems. A total of three ligands was found to bond strongly to HSO4−. We also measured the rate coefficients for NO3− clustering to HNO3 as a function of pressure. This rate was found to saturate at a value of 2.6×10−10 cm3 s−1 at a pressure of about 0.3 torr. The data were used to check the identities of some of the ions observed in the stratosphere and to predict the abundances of other ions that have not yet been observed. HNO3 concentrations derived from in situ ion composition measurements have been corrected to account for the saturation of the rate coefficient at a value less than 10−9 cm3 s−1. The corrected concentrations do not change much at 34 km but increase by a factor of almost 2 at 40.8 km. This result is in better agreement with model calculations.