Because of its fundamental importance in many branches of science, hydrogen bonding is a subject of intense contemporary research interest. The physical and chemical properties of hydrogen bonds in the ground state have been widely studied both experimentally and theoretically by chemists, physicists, and biologists. However, hydrogen bonding in the electronic excited state, which plays an important role in many photophysical processes and photochemical reactions, has scarcely been investigated.Upon electronic excitation of hydrogen-bonded systems by light, the hydrogen donor and acceptor molecules must reorganize in the electronic excited state because of the significant charge distribution difference between the different electronic states. The electronic excited-state hydrogen-bonding dynamics, which are predominantly determined by the vibrational motions of the hydrogen donor and acceptor groups, generally occur on ultrafast time scales of hundreds of femtoseconds. As a result, state-of-the-art femtos...

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Hydrogen Bonding in the Electronic Excited State

The time-dependent quantum wave packet approach has been improved and formulated to treat the multiple surface problems and thus provided a new simple, yet a clear quantum picture for interpreting the reaction mechanism underlying the nonadiabatic dynamical processes. The method keeps the salient feature of the original quantum wave packet theory developed for single surface problems, i.e. the introduction of the absorbing potential and the grid basis including the discrete variable representation and the fast Fourier transformation, which makes the present methodology a very efficient implement for the nonadiabatic quantum scattering calculations. Here, we review the theoretical basis of this approach and its applications to the fundamental triatomic chemical reactions, the latter include the nonadiabatic dynamics calculations on the F + H2, F + HD, F + D2, O(1D) + N2, O(3P, 1D) + H2, D+ + H2, and H+ + D2 reactions. We also present a thorough historical overview of the theoretically nonadiabatic dynamica...

The time-dependent quantum wave packet approach to the electronically nonadiabatic processes in chemical reactions

Complex absorbing potentials

This review discusses recent quantum scattering calculations on bimolecular chemical reactions in the gas phase. This theory provides detailed and accurate predictions on the dynamics and kinetics of reactions containing three atoms. In addition, the method can now be applied to reactions involving polyatomic molecules. Results obtained with both time-independent and time-dependent quantum dynamical methods are described. The review emphasises the recent development in time-dependent wave packet theories and the applications of reduced dimensionality approaches for treating polyatomic reactions. Calculations on over 40 different reactions are described.

Quantum scattering calculations on chemical reactions.

It is essential to evaluate the role of Coriolis coupling effect in molecular reaction dynamics. Here we consider Coriolis coupling effect in quantum reactive scattering calculations in the context of both adiabaticity and nonadiabaticity, with particular emphasis on examining the role of Coriolis coupling effect in reaction dynamics of triatomic molecular systems. We present the results of our own calculations by the time-dependent quantum wave packet approach for H + D2 and F(2P3/2,2P1/2) + H2 as well as for the ion–molecule collisions of He + H2+, D− + H2, H− + D2, and D+ + H2, after reviewing in detail other related research efforts on this issue.

Effect of Coriolis coupling in chemical reaction dynamics

In this paper, the three-dimensional time-dependent quantum wave packet calculation has been employed to study the non-adiabatic reaction dynamics of F + HD on three, electronically non-adiabatic potential energy surfaces fitted by Alexander, Stark and Werner (J. Chem. Phys., 2000, 113, 11 084; named ASW). The integral cross-sections and branching ratio of the reaction as a function of collision energy are calculated. The integral cross-sections are compared with the experimental measurements and other theoretical results. For the reaction of F in its excited state with HD, the calculated function of integral cross sections as collision energy shows that a steplike feature near 0.9 kcal mol−1 probably arises from the collinear FHD geometry.

Calculations of the F?+?HD reaction on three potential energy surfaces

Time-dependent (TD) quantum dynamics calculation for the title reaction has been carried out in full mathematical (six) dimensions on a new potential energy surface (denoted TSH3). Our numerical calculation shows that as far as total reaction probabilities and cross sections are concerned, the CN vibration behaves like a spectator bond when both reagents are at ground vibrational state. The vibrational excitation of CN slightly decreases the reaction probability and cross section while vibrational excitation of H2 considerably enhances the reaction probability and cross section. The reaction probability is enhanced by excitations of H2 rotation and more so of CN rotation. Overall, the reaction proceeds by a direct abstraction path without contribution from the insertion process. Comparison of our calculated rate constant with experimental measurements indicates that the effective barrier of the TSH3 PES for the title reaction is perhaps too high by about 0.3 kcal/mol.

Quantum dynamics study of H2+CN → HCN+H reaction in full dimensions

In this paper, we present a time-dependent quantum wave packet calculation based on the Alexander-Stark-Werner (ASW) potential energy surfaces (PESs) to study the reactivity of the ground and excited spin-orbit states for the reaction of F(P-2(3/2),P-2(1/2)) with D-2 (nu = j = 0). The reaction probabilities and the integral cross sections are calculated. Furthermore, the multistate cross sections are compared with the single-state calculation. The multistate cross section is smaller than the single-state calculation at higher collision energy. The effect of the nonadiabatic coupling becomes more and more obvious as the collision energy increases. The overall reactivity of the excited state of F is, at most, 25% of that of the ground spin-orbit states. The threshold energy of the F(P-2(3/2)) + D-2 reaction is similar to0.10 kcal/mol. The contributions of the excited state of F are 0.9% and 3.1% of the total average rate constant, at 200 and 500 K, respectively. The effect of the excited spin-orbit state rate constant to the average rate constant is very small but grows slowly as the temperature increases.

Reactivity of the ground and excited spin-orbit states for the reaction of the F(2P3/2, 2P1/2) with D2

The state-to-state dynamics of the H+D2 reaction is studied by the reactant-product decoupling method using the double many-body expansion potential energy surface. Two approaches are compared: one uses only the lowest adiabatic sheet while the other employs both coupled diabatic sheets. Rotational distributions for the reaction H+D2 (υ=0,j=0)→HD(υ′=3,j′)+D are obtained at eight different collision energies between 1.49 and 1.85eV; no significant difference are found between the two approaches. Initial state-selected total reaction probabilities and integral cross sections are also given for energies ranging from 0.25 up to 2.0eV with extremely small differences being observed between the two sets of results, thus showing that the nonadiabatic effects in the title reaction are negligible at least for small energies below 2.0eV.

Yan Zhang

Papers

The time-dependent quantum wave packet approach to the electronically nonadiabatic processes in chemical reactions

Calculations of the F?+?HD reaction on three potential energy surfaces

Quantum dynamics study of H2+CN → HCN+H reaction in full dimensions

Reactivity of the ground and excited spin-orbit states for the reaction of the F(2P3/2, 2P1/2) with D2

Nonadiabatic effects in the H+D2 reaction.