Theoretical modeling of postionization fragmentation of rare-gas trimer cations

Abstract

The dynamics of ionic rare-gas trimers (Ar(3) (+), Kr(3) (+), and Xe(3) (+)) produced by a sudden ionization of neutral precursors is investigated theoretically with a hybrid classical-quantum method for solving the equations of motion governed by a Hamiltonian obtained from a previously tested diatomics-in-molecules model. Initial conditions are selected with Monte Carlo sampling. Two possibilities for generating the initial electronic state are considered: diabatic (local) and adiabatic (delocalized). The dynamics generally leads to fragmentation, producing either monomer ions or dimer ions in a relatively short time; however, a large number of long-lived metastable trimer ions are also seen in some cases. We have analyzed the dynamics with respect to the fraction of monomer ions produced, the distribution of the kinetic energy of the products, and the distribution of fragmentation times of the trimers. Initial diabatic ionization is associated with much faster fragmentation than adiabatic ionization. Spin-orbit coupling plays an important role in the fragmentation dynamics.

Photodissociation dynamics of ionic argon pentamer

“…Unfortunately, no experiments have been carried out at these photon energies to be compared with. We have also observed a similar situation for krypton and xenon clusters [32], where trimers with very long nonradiative life times were found in our simulations on the post-ionization fragmentation at energies for which the atomic fragments switch from the lower fine-structure state ( 2 P 3/2 ) to the higher one ( 2 P 1/2 ). Without the spin-orbit interactions included, these metastable trimers are almost not produced.…”

“…2 and 3, rewritten in matrix form as well as details on the implementation of these equations are given in Ref. 32. In accordance with our previous studies, we denote this dynamical model as MF (Mean-Field) throughout this work.…”

“…In this work we use the diatomic curves for Ar + 2 taken from ab initio calculations [28], a state-of-the-art semiempirical potential for neutral Ar 2 [29], and the spin-orbit coupling constant extracted from experimental data on the splitting between the 2 P 1/2 and 2 P 3/2 fine-structure states of Ar + [30]. The DIM+SO model used in this work has many times been tested successfully against available experimental data on small and medium-size argon clusters, including their structures and energetics [6,31], photoabsorption [6], and non-adiabatic dynamics [14,15,32], and can, thus, be considered well established for the description of intra-cluster interactions in these clusters.…”

“…10-12, and extended recently [32] by the inclusion of the spin-orbit interaction. A detailed overview of the equations of motions, Eqs.…”

Vibrational spectrum of Ar3+ and relative importance of linear and perpendicular isomers in its photodissociation

“…This process leads to an ionized trimer at a not well defined rovibrational temperature, but probably with significant internal energy [38]. A more realistic way of the modeling of distributions of Ar + 3 rovibronic states prior to photoexcitation, namely injecting the output of post-ionization fragmentation simulations [39][40][41][42][43] into photodynamics calculations, is not possible at present due to the lack of relevant post-ionization fragmentation data and will require more extensive and detailed investigations in the future.…”