Molecular dynamics of photodissociation in matrices including nonadiabatic processes

Abstract

Molecular dynamics calculations of the photodissociation of HCl and C1 2 in a Xe crystal have been performed using diatomics-in-molecules (DIM) Hamiltonians to describe the electronic interaction. Nonadiabatic transitions between the adiabatic states are explicitly taken into account in the equations of motion. It is shown that the transitions occur on a subpicosecond-time scale. They induce fast recombination of the fragments, thus leading to a reduction of the quantum yield of permanent dissociation. In addition to the octahedral and tetrahedral interstitial sites the DIM model predicts two further energy minima for Cl in a Xe crystal. One of them, a D2 site between two neighboring xenon atoms, is populated after dissociation of Cl 2 . In this case, our calculations led to recombination of the molecule when the system is annealed at temperatures below the onset of thermal diffusion of Cl atoms.

Power dissipation in nanoscale conductors: classical, semi-classical and quantum dynamics

“…To answer it we need to know how the electronic and atomic dynamics are coupled. This coupling has been investigated widely in a number of other contexts, such as non-radiative transitions [8] and photodissociation [9,10,11], and many methods of varying complexity and ingenuity have been developed. The range of methods is a testament to the fact that it is exceedingly difficult to obtain good results using available computer resources, except for model problems.…”

Cage effect for the photodissociation of H2O molecules in argon clusters embedded inside neon clusters

“…The balance between exit and reentry processes is of importance in H 2 O@Rg matrices, at least for light dissociation products, like H atoms. 1,2,15 Second, the study of size effects enables us to observe the building process of the cage.…”

Photodissociation Dynamics of Molecular Fluorine in an Argon Matrix Induced by Ultrashort Laser Pulses

“…The time evolution of the photoexcited F 2 @Ar system is described by two coupled time-dependent Schrödinger equations for the wave functions ψ g (R F2 ,R Ar3 ,t) and ψ e (R F2 ,R Ar3 ,t) corresponding to the nuclear motions in the ground and excited electronic state where the semiclassical expression for the interaction Hamiltonian (9) has been used (with the transition dipole depending on R F2 only) and where the kinetic energy operator is given by with reduced masses m F2 ) m F /2 and m Ar3 ) 6m Ar . Note that the latter mass has been derived by forming symmetry-adapted linear combinations (A 1g representation of the D 3d point group) of the motions of the six Ar atoms perpendicular to the 〈111〉 axis using the method of projection operators.…”

“…As a compromise, we resort to the diatomics-in-molecule (DIM) approximation, 25 which has been frequently used in molecular dynamics simulations of atomic and molecular impurities in rare gas solids. 3,9,11,12,16,20 In principle, such an approach can account for the anisotropy of the electron densities of open shell atoms. In the following we give a brief overview of the DIM ansatz; for a detailed description of the DIM Hamiltonian for F2@Ar we refer to the work presented in ref 23.…”

“…This situation is typically encountered for the smallest photofragments such as hydrogen atoms. 2,[7][8][9][10][11][12][13][14] For larger rare gases (Kr, Xe) sudden cage exit was also reported for F atoms. [15][16][17][18][19] In contrast, for large and heavy fragments with high excess energy, the momentum transferred in collisions with the environment may be sufficient to displace cage particles, thus opening a new path for the exit of photofragments by scrambling solvent particles and solute fragments.…”