A COMPARISON OF AN EXPERIMENTAL UNIMOLECULAR LIFETIME DISTRIBUTION WITH RICE-RAMSPERGER-KASSEL-MARCUS THEORY

The ion-molecule association system (CH3+/CH3CN) has been reexamined b y the ion cyclotron double resonance technique. An experimental distri bution of lifetimes has been measured for the collision complex (CH3CN CH3+) formed in the association reaction between CH3+ and CH3CN. The experimental mean lifetime of the association complex formed within th e ICR cell was 140 mus. A theoretical examination of the distribution of complex lifetimes using an RRKM model was also undertaken. The matr ix of lifetimes for the various values of the total energy of the syst em (E) and the total angular momentum of the system (J) was obtained. This information was used to visualize the canonical ensemble of colli sion complexes in the ICR experiment in terms of their lifetimes. Once the distribution of lifetimes predicted by the model was modified to conform to experimental constraints, it was found to give a good appro ximation of the lifetime distribution determined experimentally. As a result of the new measurements of the complex lifetimes, we report abs olute values of the collisional stabilization efficiencies. We also re port rate coefficients for unimolecular dissociation and radiative rel axation.