Final state-resolved mode specificity in HX + OH → X + H₂O (X = F and Cl) reactions: A quasi-classical trajectory study

Abstract

The state-to-state dynamics of the title reactions are investigated using a quasi-classical trajectory method on recently developed accurate global potential energy surfaces. Although both produce the H2O product, these two reactions have very different characteristics in the reaction energy, barrier location, and barrier height. It is shown that the H2O product is moderately excited in its three vibrational modes in the HF + OH reaction, but its stretching modes are highly excited in the HCl + OH reaction. For both reactions, the OH vibrational degree of freedom is essentially a spectator, which sequesters its energy throughout the reaction. On the other hand, the HF vibrational excitation has almost no impact on the H2O vibrational distribution while HCl converts some of its vibrational energy into the stretching modes of H2O. These mode specific correlations can be rationalized by the recently proposed Sudden Vector Projection model.

Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal

“…In addition, the efficacies of the symmetric and antisymmetric stretching modes are quite similar, and both are larger than that for translation. These observations are consistent with our earlier initial state specific QD study 28 as well as state-to-state QCT results, 25,26 in terms of the mode specificity.…”

“…Very recently, we have reported quasi-classical trajectory (QCT) and initial state specific quantum dynamical (QD) calculations of the title reaction and its reverse using a recently developed global PES based on ab initio calculations. [24][25][26][27][28] The state-to-state quantum dynamical calculations reported here are made possible using a transition-state wave packet (TSWP) method recently proposed by Manthe and coworkers, [29][30][31] which is an extension of Miller's quantum transition-state theory. 32,33 Our implementation of this method has been discussed in detail elsewhere, 16,34 so only a brief outline is given here.…”

Dissection of the Multichannel Reaction O(3P) + C2H2: Differential Cross-Sections and Product Energy Distributions

“…For polyatomic products, the normal mode analysis (NMA) method [ 37 , 38 , 39 , 40 , 41 ] based on the harmonic approximation and the decoupling of all degrees of freedom was applied to gain quantum-like vibrational states. In the NMA method, the coordinates and momenta, extracted from one step of the last period that has the minimum potential energy of each reactive trajectory, are taken as input.…”

Vibrational State-to-State Scattering of Water from Cu(111): Comparison of Quantum and Quasiclassical Methods with Normal Mode and Adiabatic Switching Sampling

“…That is to say, one needs to find a rotational matrix D that minimizes || Dq – Q ref || 2 (or equivalently satisfies the rotational Eckart condition). Here, our implementation is essentially the same as that in ref using a quaternion-based method . Normal mode coordinates Q and momenta P can then be obtained by the normal mode transformation from the mass-weighted Cartesian displacement coordinates and momenta where L is the transformation matrix between the normal mode and Cartesian displacement coordinates, q ′ = Dq – q ref , p′ = Dp .…”