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

Abstract

The electronic excitation induced by ultrashort laser pulses and the subsequent photodissociation dynamics of molecular fluorine in an argon matrix are studied. The interactions of photofragments and host atoms are modeled using a diatomics-in-molecule Hamiltonian. Two types of methods are compared: (1) quantumclassical simulations where the nuclei are treated classically, with surface-hopping algorithms to describe either radiative or nonradiative transitions between different electronic states, and (2) fully quantum-mechanical simulations, but for a model system of reduced dimensionality, in which the two most essential degrees of freedom are considered. Some of the main results follow: (1) The sequential energy transfer events from the photoexcited F 2 into the lattice modes are such that the "reduced dimensionality" model is valid for the first 200 fs. This, in turn, allows us to use the quantum results to investigate the details of the excitation process with short laser pulses. Thus, it also serves as a reference for the quantum-classical "surface hopping" model of the excitation process. Moreover, it supports the validity of a laser pulse control strategy developed on the basis of the "reduced dimensionality" model. (2) In both the quantum and quantum-classical simulations, the separation of the F atoms following photodissociation does not exceed 20 bohr. The cage exit mechanisms appear qualitatively similar in the two sets of simulations, but quantum effects are quantitatively important. (3) Nonlinear effects are important in determining the photoexcitation yield. In summary, this paper demonstrates that quantum-classical simulations combined with reduced dimensionality quantum calculations can be a powerful approach to the analysis and control of the dynamics of complex systems.

Water-Related Matrix Isolation Phenomena during NO2 Photolysis in Argon Matrix

“…In addition, O atoms move through the argon matrix to react with O 2 to produce ozone. 24 The mobility of O and NO radicals may occur either through lattice defects as mentioned by Ford et al, 10 or delayed cage exit as discussed by Chaban et al 25 In the latter case, the existing argon windows enlarge due to the collisions of the photo-fragmented species with the argon atoms. This allows NO and O species to escape due to the lower energy barrier for cage exit without rearranging the particles.…”

A potential energy surface and a trajectory study of photodynamics and strong-field alignment of ClF molecule in rare gas (Ar,Kr) solids

“…Prior to high-level quantum evaluation of, for example, the rotational or vibrational coordinates of the molecule, by solving the time-dependent Schro ¨dinger equation, it is of key importance to know the proper conditions. With this guide, reduceddimensionality approaches [21][22][23][24][25] necessary for quantum description in large systems can be used. Here, we present a classical mechanics description to calculate observables of the ground and excited state ClF molecule in Ar and Kr solids, dictated by the input potentials for atom-atom interactions and the adopted computational method.…”

Ultrafast dynamics of halogens in rare gas solids

“…This has been studied in atomic fragment calculations 36 and nonadiabatic dynamics simulations for the F 2 molecule. [123][124][125] Fig. 2 presents the difference in potential energy barriers between orientations toward tetra-atomic and triatomic windows for the stretching ClF molecule in Ar.…”