Reaction resonances, or transiently stabilized transition-state structures, have proven highly challenging to capture experimentally. Here, we used the highly sensitive H atom Rydberg tagging time-of-flight method to conduct a crossed molecular beam scattering study of the F + H2 --> HF + H reaction with full quantum-state resolution. Pronounced forward-scattered HF products in the v' = 2 vibrational state were clearly observed at a collision energy of 0.52 kcal/mol; this was attributed to both the ground and the first excited Feshbach resonances trapped in the peculiar HF(v' = 3)-H' vibrationally adiabatic potential, with substantial enhancement by constructive interference between the two resonances.

Graphene nanosheet-supported ultrafine metal nanoparticles encapsulated by thin mesoporous SiO2 layers were prepared and used as robust catalysts with high catalytic activity and excellent high-temperature stability. The catalysts can be recycled and reused in many gas- and solution-phase reactions, and their high catalytic activity can be fully recovered by high-temperature regeneration, should they be deactivated by feedstock poisoning. In addition to the large surface area provided by the graphene support, the enhanced catalytic performance is also attributed to the mesoporous SiO2 layers, which not only stabilize the ultrafine metal nanoparticles, but also prevent the aggregation of the graphene nanosheets. The synthetic strategy can be extended to other metals, such as Pd and Ru, for preparing robust catalysts for various reactions.

Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique that produces high-resolution (time-resolved) vibrational spectra from either the ground or excited electronic states of molecules, free from background fluorescence. FSRS uses simultaneously a narrow bandwidth ∼1 -3 ps Raman pump pulse with a continuum ∼30-50 fs Stokes probe pulse to produce sharp Raman gains, at positions corresponding to vibrational transitions in the sample, riding on top of the continuum Stokes probe spectrum. When FSRS is preceded by a femtosecond actinic pump pulse that initiates the photochemistry of interest, time-resolved Raman spectroscopy can be carried out. We present two theoretical approaches to FSRS: one is based on a coupling of Raman pump and probe light waves with the vibrations in the medium, and another is a quantum-mechanical description. The latter approach is used to discuss the conditions of applicability and limitations of the coupled-wave description. Extension of the quantum-mechanical description to the case where the Raman pump beam is on resonance with an excited electronic state, as well as when FSRS is used to probe a nonstationary vibrational wave packet prepared by an actinic pump pulse, is also discussed.

Aqueous batteries (ABs) have attracted increasing attention because of their inherent safety and low cost. Nevertheless, hydrogen evolution reaction (HER) at the anode presents severe challenges for stable and safe operation of ABs. Instead of passivating the anode surface to hinder HER kinetics, a novel design strategy is proposed here to suppress the HER via alternating its thermodynamics pathway. By adding a hydrogen bond acceptor, dimethyl sulfoxide (DMSO), the onset potential of HER can be delayed by as much as 1.0 V (on titanium mesh). Spectral characterization and molecular dynamics simulation confirm that the formation of hydrogen bonds between DMSO and water molecules can reduce the water activity, thereby suppressing the HER. This strategy has proven to be universal in expanding the electrochemical window of aqueous electrolytes. For instance, unconventional V 2+ ↔V 3+ redox processes in Na 3 V 2 (PO 4 ) 3 (-1.2 V versus Ag/AgCl) and highly stable Zn plating/stripping processes can be realized in ABs.

Graphene nanosheet-supported ultrafine metal nanoparticles encapsulated by thin mesoporous SiO 2 layers were prepared and used as robust catalysts with high catalytic activity and excellent high-temperature stability. The catalysts can be recycled and reused in many gas-and solution-phase reactions, and their high catalytic activity can be fully recovered by high-temperature regeneration, should they be deactivated by feedstock poisoning. In addition to the large surface area provided by the graphene support, the enhanced catalytic performance is also attributed to the mesoporous SiO 2 layers, which not only stabilize the ultrafine metal nanoparticles, but also prevent the aggregation of the graphene nanosheets. The synthetic strategy can be extended to other metals, such as Pd and Ru, for preparing robust catalysts for various reactions.

There has been great progress in the development of potential energy surfaces (PESs) and quantum dynamics calculations in the gas phase. The establishment of a fitting procedure for highly accurate PESs and new developments in quantum reactive scattering on reliable PESs allow accurate characterization of reaction dynamics beyond triatomic systems. This review will give the recent development in our group in constructing ab initio PESs based on neural networks and the time-dependent wave packet calculations for bimolecular reactions beyond three atoms. Bimolecular reactions of current interest to the community, namely, OH + H, H + HO, OH + CO, H + CH, and Cl + CH, are focused on. Quantum mechanical characterization of these reactions uncovers interesting dynamical phenomena with an unprecedented level of sophistication and has greatly advanced our understanding of polyatomic reaction dynamics.

Perfect polyhedral 50-facet Cu 2 O microcrystals enclosed by high ratio exposed high-index {211}, {522} or {311} facets were successfully synthesized by a facile wet-chemical route under mild temperature and normal pressure. The morphological evolution of 50-facet Cu 2 O polyhedra was studied carefully and in detail by adjusting reaction parameters such as reaction temperature, reaction time, the concentration and type of alkali metal hydroxides and copper salts, and the amount of the reduction agent glucose. On the basis of these results, a formation mechanism of these polyhedra was tentatively proposed. As compared with Cu 2 O cubes and octahedra with low-index {100} and {111} facets, respectively, the as-prepared 50-facet Cu 2 O polyhedra showed higher photocatalytic activities towards the decomposition of the organic dye methyl orange due to more catalytic active sites being held in the high-index facets.

The effect of the time delay between the picosecond Raman pump and the femtosecond Stokes probe pulse on the Raman gain line shape in femtosecond broadband stimulated Raman spectroscopy (FSRS) is presented. Experimental data are obtained for cyclohexane to investigate the dependence of the FSRS line shape on this time delay. Theoretical simulations of the line shapes as a function of the time delay using the coupled wave theory agree well with experimental data, recovering broad line shapes at positive time delays and narrower bands with small Raman loss side wings at negative time delays. The analysis yields the lower bounds of the vibrational dephasing times of 2.0 ps and 0.65 ps for the 802 and 1027 cm −1 modes for cyclohexane, respectively. The theoretical description and simulation using the coupled wave theory are also consistent with the observed Raman gain intensity profile over time delay, reaching the maximum at a slightly negative time delay (∼−21 ps), and show that the coupled wave theory is a good model for describing FSRS.