Translational and internal energy dependences of some ion–neutral reactions

Abstract

The forward and reverse rate constants for the proton-transfer reaction, N2OH++CO?COH++N2O, have been measured as a function of temperature in a variable-temperature flowing afterglow and as a function of relative kinetic energy in a flow-drift tube using both helium and argon buffer gases. The temperature variation of the rate constant was used to obtain ΔH0 =−4.4±0.4 kcal/mole and ΔS0=−4.0±1.0 entropy units. Furthermore, the comparison of the data taken as a function of temperature with those taken as a function of relative kinetic energy in different buffer gases shows that there are marked effects of ion vibrational energy on these rate constants. Similar data on the charge–transfer reaction, CO2++O2→O2++CO2, show the same effects. In addition, relative kinetic energy data on the proton transfer, ArH++O2→O2H++Ar, also imply strong effects of vibrational excitation on the rate constant.