Rate constants for the reactions of ions with dipolar polyatomic molecules

Abstract

Calculations of rate constants for the reactions of N⁺ with NH₃ and H₂O are presented. A combined rotationally adiabatic capture and centrifugal sudden approximation is used. The results are compared with those obtained in CRESU measurements at 27, 68 and 163 K, and SIFT experiments at 300 K. For the N⁺+ H₂O reaction, the agreement between both sets of experimental results and the calculations is excellent. For the N⁺+ NH₃ reaction, our calculation agrees well with the SIFT result at 300 K, but the CRESU rate constants fall below the calculated values. Both experimental and theoretical rate constants show a strong negative temperature dependence. The sensitivity of the rate constants to the initial rotational states j and K is examined.