Unimolecular dynamics of Cl⁻...CH₃Cl intermolecular complexes formed by Cl⁻+CH₃Cl association Available to Purchase

A previous trajectory study of the dissociation of Cl⁻...CH₃Cl complexes formed by Cl⁻+CH₃Cl association is further analyzed to determine (1) the relationship between classical and quantum Rice–Ramsperger–Kassel–Marcus (RRKM) rate constants for Cl⁻...CH₃Cl→Cl⁻+CH₃Cl dissociation; (2) the importance of anharmonicity in calculating the RRKM dissociation rate constant; (3) the role of angular momentum in interpreting the trajectory distribution N(t)/N(0) of Cl⁻...CH₃Cl complexes versus time; and (4) the pressure‐dependent collision‐averaged rate constant k(ω,E) for Cl⁻...CH₃Cl dissociation. It is found that only the low‐frequency intermolecular modes of Cl⁻...CH₃Cl are initially excited by Cl⁻+CH₃Cl association. Classical and quantum RRKM rate constants for dissociation of this intermolecular complex are in excellent agreement. Anharmonicity lowers the rate constant by a factor of 4–8 from its harmonic value. The dissociation rate for the long‐time tail of the trajectory N(t)/N(0) distribution is much smaller than predicted by a RRKM model, which accurately treats angular momentum. It is suggested that the long‐lived trajectories may arise from motion on vague tori. The trajectory collision‐averaged rate constant k(ω,E) is in agreement with an experimental study at 300 K.