POLYATOMIC ION-MOLECULE RADIATIVE ASSOCIATION - THEORETICAL FRAMEWORK AND PREDICTIONS - OBSERVATIONS OF NO++C6H5CN AS AN EXAMPLE

A theoretical estimation scheme is described for the radiative association of ions with polyatomic molecules. The rate estimate is based on calculation of the competing processes of redissociation and radiative stabilization of the initial collision complex. Following the definition of a standard hydrocarbon whose properties should approximate those of many real molecules, Ramsperger-Rice-Kassel-Marcus kinetics are used to estimate the redissociation rate, and the IR radiative rate is estimated using established methods. The numbers found in this way are shown to be a useful predictor of the order of magnitude of the radiative association efficiency for a number of known systems. The radiative association of NO+ with benzonitrile was predicted to be reasonably efficient. This process was observed in the ion cyclotron resonance (ICR) spectrometer, and was found to have an efficiency per collision of 0.014, and a rate of photon radiation from the collision complex of 29 s-1, in excellent agreement with the theoretical estimates. © 1990.