Explore the vast range of titles available.

The Born–Oppenheimer approximation, assuming separable nuclear and electronic motion, is widely adopted for characterizing chemical reactions in a single electronic state. However, the breakdown of the Born–Oppenheimer approximation is omnipresent in chemistry, and a detailed understanding of the non-adiabatic dynamics is still incomplete. Here we investigate the non-adiabatic quenching of electronically excited OH(A2Σ+) molecules by H2 molecules using full-dimensional quantum dynamics calculations for zero total nuclear angular momentum using a high-quality diabatic-potential-energy matrix. Good agreement with experimental observations is found for the OH(X2Π) ro-vibrational distribution, and the non-adiabatic dynamics are shown to be controlled by stereodynamics, namely the relative orientation of the two reactants. The uncovering of a major (in)elastic channel, neglected in a previous analysis but confirmed by a recent experiment, resolves a long-standing experiment–theory disagreement concerning the branching ratio of the two electronic quenching channels.The breakdown of the Born–Oppenheimer approximation is omnipresent in chemistry and detailed understanding of non-adiabatic dynamics is still incomplete. Now, the non-adiabatic quenching of electronically excited OH(A2Σ+) molecules by H2 has been investigated using full-dimensional quantum dynamics calculations and a high-quality diabatic-potential-energy matrix, providing insight into the branching ratio of the two electronic quenching channels.

How the non-reacting moiety of a molecule influences a polyatomic reaction has been a topic of much research interest. Here we present a comprehensive investigation of the D + CH 4  → HD + CH 3 reaction, a benchmark polyatomic elementary reaction with CH 3 as the non-reacting moiety, employing a high-resolution crossed molecular beams apparatus and an accurate seven-dimensional wave packet method. An interesting angular distribution of the CH 3 ( v’  = 1) product umbrella bending vibrational state is observed to scatter more in the sideways direction than the CH 3 ( v’  = 0) one. By monitoring the wave functions on a dividing surface in the transition state region, the CH 3 umbrella bending mode is established as a reporter mode that faithfully reveals how the D atom dynamically approaches CH 4 at different total angular momenta or impact parameters. This discovery of the reporter mode provides an opportunity for the detailed study of polyatomic reaction dynamics. The effects of non-reacting components on polyatomic reactions are still largely unclear. Here, the authors show through a combined experimental and theoretical study of the D + CH 4 reaction that the CH 3 umbrella bending mode serves as a reporter mode, revealing how the D atom dynamically approaches CH 4 .

A full-dimensional quantum dynamics simulation of a hydrogen atom reacting with methane on an accurate ab initio potential energy surface is reported. Based on first-principles theory, thermal rate constants are predicted with an accuracy comparable to (or even exceeding) experimental precision. The theoretical prediction is within the range of the significantly varied experimental rate constants reported by different groups. This level of accuracy has previously been achieved only for smaller, three-or four-atom reactive systems. Comparison with classical transition state theory confirms the importance of quantum mechanical tunneling for the rate constant below 400 kelvin.

How the non-reacting moiety of a molecule influences a polyatomic reaction has been a topic of much research interest. Here we present a comprehensive investigation of the D + CH  → HD + CH reaction, a benchmark polyatomic elementary reaction with CH as the non-reacting moiety, employing a high-resolution crossed molecular beams apparatus and an accurate seven-dimensional wave packet method. An interesting angular distribution of the CH (v' = 1) product umbrella bending vibrational state is observed to scatter more in the sideways direction than the CH (v' = 0) one. By monitoring the wave functions on a dividing surface in the transition state region, the CH umbrella bending mode is established as a reporter mode that faithfully reveals how the D atom dynamically approaches CH at different total angular momenta or impact parameters. This discovery of the reporter mode provides an opportunity for the detailed study of polyatomic reaction dynamics.

The multi-layer multi-configurational time-dependent Hartree (MCTDH) in optimized second quantization representation (oSQR) approach combines the tensor contraction scheme of the multi-layer MCTDH approach with the use of an optimized time-dependent orbital basis. Extending the original work on the subject [Manthe, Weike, J. Chem. Phys. 146, 064117 (2017)], here MCTDH-oSQR propagation in imaginary time and properties related to particle number conservation are studied. Difference between the orbital equation of motion in real and imaginary time are highlighted and a new gauge operator which facilitates efficient imaginary time propagation is introduced. Studying Bose-Hubbard models, particle number conservation in MCTDH-oSQR calculations is investigated in detail. Interesting properties of the single-particle functions used in the multi-layer MCTDH representation are identified. Based on these results, a tensor contraction scheme which explicitly utilizes particle number conservation is suggested.

A full-dimensional quantum dynamics simulation of a hydrogen atom reacting with methane on an accurate ab initio potential energy surface is reported. Based on first-principles theory, thermal rate constants are predicted with an accuracy comparable to (or even exceeding) experimental precision. The theoretical prediction is within the range of the significantly varied experimental rate constants reported by different groups. This level of accuracy has previously been achieved only for smaller, three- or four-atom reactive systems. Comparison with classical transition state theory confirms the importance of quantum mechanical tunneling for the rate constant below 400 kelvin.

A full-dimensional quantum dynamics simulation of a hydrogen atom reacting with methane on an accurate ab initio potential energy surface is reported. Based on first-principles theory, thermal rate constants are predicted with an accuracy comparable to (or even exceeding) experimental precision. The theoretical prediction is within the range of the significantly varied experimental rate constants reported by different groups. This level of accuracy has previously been achieved only for smaller, three- or four-atom reactive systems. Comparison with classical transition state theory confirms the importance of quantum mechanical tunneling for the rate constant below 400 kelvin. [PUBLICATION ABSTRACT]

A full-dimensional quantum dynamics simulation of a hydrogen atom reacting with methane on an accurate ab initio potential energy surface is reported. Based on first-principles theory, thermal rate constants are predicted with an accuracy comparable to (or even exceeding) experimental precision. The theoretical prediction is within the range of the significantly varied experimental rate constants reported by different groups. This level of accuracy has previously been achieved only for smaller, three- or four-atom reactive systems. Comparison with classical transition state theory confirms the importance of quantum mechanical tunneling for the rate constant below 400 kelvin.

A full-dimensional quantum dynamics simulation of a hydrogen atom reacting with methane on an accurate ab initio potential energy surface is reported. Based on first-principles theory, thermal rate constants are predicted with an accuracy comparable to (or even exceeding) experimental precision. The theoretical prediction is within the range of the significantly varied experimental rate constants reported by different groups. This level of accuracy has previously been achieved only for smaller, three-or four-atom reactive systems. Comparison with classical transition state theory confirms the importance of quantum mechanical tunneling for the rate constant below 400 kelvin.