Vibrational Energy Exchange of Highly Excited Anharmonic Oscillators

Abstract

The probabilities of dissociation P_dis, excitation P_ex, de‐excitation P_de, and the associated average energy exchanges were calculated theoretically for a highly energized, anharmonic oscillator (I₂ or Br₂) colliding classically with an inert gas atom C through a Morse‐type potential. The effect of varying mass and well depth was investigated. It was found that the effect of anharmonicity is to favor excitation and dissociation. However, the average ΔE_v for these processes is about the same for harmonic and anharmonic oscillators and not much bigger than 1 to 2 RT. P_dis increases markedly with increasing mass. The well depth (V₀) does not seem to have much effect in the range 0.004<V₀/D₀D₀ is the bond dissociation energy. Exchange reactions are observed, but for shallow well depths they are rare events. From the results, it is possible to calculate λ, the probability of stabilizing an atom pair by a third‐body collision. This turns out to be independent of temperature but depends strongly on the mass of the third body C. It is always in the range 0.1<λRT) above the dissociation barrier. This implies an activation energy for dissociation of the order of D₀°—2RT in the Benson—Fueno theory and also a T^—2 dependence for the rate of recombination of atoms.