Molecular Dynamics of Photodissociation: Quasidiatomic Model for ICN

Abstract

A model for the photodissociation of ICN in its lowest continuum is developed and is used to predict the partitioning of available energy between translational, rotational, and vibrational energies of the recoiling fragments. The model is based on three major assumptions: (i) that only one upper electronic state is involved, (ii) that light absorption affects only the breaking C–I bond, thus allowing the upper-state potential surface to be calculated quasidiatomically from spectral and thermodynamic data, and (iii) that the mechanics of the “half-collision” of the recoiling fragments on this potential surface may be treated as classical to predict the average partitioning between translational, rotational, and vibrational energies, and by a classical-energy forced quantum oscillator approximation to predict the partitioning between vibrational states. The model predicts that most of the available energy will go into translation, which is consistent with flash photolysis studies and with crude measurements of the photofragment spectrum.

Fragmentation of valence electronic states of CF3–CH2F+and CHF2–CHF2+in the range 12–25 eV

“…These models, with original source references, are described in detail in our recent work on dissociative photoionisation of CHF 2 −CF 3 [6] and elsewhere. [35] The experimentallydetermined values of <KE> T and f T are shown in Table 3, together with calculated values of f T for statistical [36] and pure-impulsive [37] dissociation models. Since many of the vibrational frequencies of the fragment ions are unknown, statistical values for f T were calculated according to the lower limit value of 1/(x+1), where x is the number of vibrational degrees of freedom in the transition state of the unimolecular reaction.…”

Molecular dynamics of the A+BC reaction in rare gas solution

“…Similar effects can be seen in the X 2 rotational energy with a time scale of about 0.2 ps. This rotational energy is small, originating 43 from a) the repulsion of the X from the X 2 for bent original configurations, b) bend vibrational motion at the barrier, and c) the original angular momentum of the X 3 at the transition barrier.…”

Fragmentation of valence electronic states of CHF2CF3+ studied by threshold photoelectron–photoion coincidence (TPEPICO) techniques in the photon energy range 12–25 eV

“…As a consequence, there is a transfer of energy to vibrational, in addition to the possible transfer of energy to rotational, degrees of freedom of the fragments. For this model, Holdy et al [43] have shown that E avail and <KE> T are related by simple kinematics :…”