Atom–Diatom Reactive Scattering Collisions in Protonated Rare Gas Systems

Abstract

The study of the dynamics of atom–diatom reactions involving two rare gas (Rg) atoms and protons is of crucial importance given the astrophysical relevance of these processes. In a series of previous studies, we have been investigating a number of such Rg(1)+ Rg(2)H+→ Rg(2)+ Rg(1)H+ reactions by means of different numerical approaches. These investigations comprised the construction of accurate potential energy surfaces by means of ab initio calculations. In this work, we review the state-of-art of the study of these protonated Rg systems making special emphasis on the most relevant features regarding the dynamical mechanisms which govern these reactive collisions. The aim of this work therefore is to provide an as complete as possible description of the existing information regarding these processes.

Ar+ ArH+ Reactive Collisions of Astrophysical Interest: The Case of 36Ar

“…In the second type of trajectories, the rotationally excited diatom forms a weakly bound complex together with the free atom and there is not enough translational energy remaining which can dissociate the complex to form products. These are called roaming [48] trajectories and were also seen for other Ng+Ng′H + collisions [24,26–28] …”

“…( 7) are given in Ref. [28,29] Here it suffices to mention that we solve the corresponding coupled channel equations established between the total wave function and its second derivative through the interaction matrix, by means of a time independent log derivative propagation in the region defined between the capture radius R c = 5.2 Å and the asymptotic distance 22.9 Å.…”

“…These are called roaming [48] trajectories and were also seen for other Ng + Ng'H + collisions. [24,[26][27][28]…”

“…[24] and a variety of computational approaches, such as quantum, statistical and quasi‐classical ones, to examine the influence, if any, of the isotopic substitution. In particular, our previous studies performed on Ng$${^{\left( 1 \right)} }$$ +Ng$${^{\left( 2 \right)} }$$ H$${^ + \to }$$ Ng$${^{\left( 2 \right)} }$$ +Ng$${^{\left( 1 \right)} }$$ H + reactions, [25–28] where Ng stands for a noble gas atom, have shown that the presence of a relatively deep well in the intermediate region of the Ng 2 H + PESs, between the reactants and products, suggests the importance of complex‐forming mechanisms on the overall dynamics. Statistical techniques have been found to provide a fair description of the QM results for these processes.…”

High-resolution electronic and vibrational spectroscopy of small-to-medium sized molecules with ab initio potential energy surface

“…For the near dissociation states of these atom-diatom complexes, the mixing between the diatomic ro-vibrational levels with the total system ro-vibrational levels is small, and the diatomic ro-vibrational states can still be treated as useful quantum numbers [37]. This type of collision complex has been observed for protonated rare gas systems as well as many other chemical reactions in the quasiclassical trajectory simulations [103,104]. The transitions between the near-dissociation states for those complexes can be observed via far IR or microwave spectroscopic experiments [105,106].…”