Bina Fu

We present the first six-dimensional quantum dynamics study of HCl dissociative chemisorption on Pt(111) based on an accurate neural network potential energy surface. The transition state H-Cl bond is stretched by Δr = 0.40 to 2.82 bohr, significantly shorter than those for HCl on Au(111) and Ag(111). This places HCl/Pt(111) in a distinct central barrier regime, leading to two atypical outcomes. First, unlike on Au(111) or Ag(111), where the top site is two orders of magnitude less reactive, the dissociation probability at the top site on Pt(111) is comparable to that at other sites. Second, translational energy is consistently more effective than vibrational excitation, with vibrational efficacy η < 1 for v = 1 and 2 across the entire total energy range. In contrast, rotational effects remain unaffected, showing the same helicopter preference and reduced rotational efficacy as on monometallic surfaces. By comparing eleven HCl + metal systems, we reveal a clear quantitative trend. When Δr is 0.40-0.50 bohr, η remains below unity. When Δr reaches 1.32 bohr, η is always above unity. This provides a geometric rationalization of Polanyi's early/late dichotomy.

Laser desorption/ionization mass spectrometry (LDI-MS) is attractive for serum and spatial metabolomics, but metabolite analysis is limited by inefficient ionization and severe low-mass interference from conventional matrices. Here we report a vacancy-clustered molybdenum oxide (MoO _x ) matrix for LDI-MS analysis of serum profiling and spatial tissue imaging. Vacancy-clustered defects, rather than vacancy-lean, point-defect-dominated, or over-reduced states, markedly enhance photogenerated charge separation and interfacial charge transport, enabling efficient metabolite ionization. This highlights vacancy organization as a key design fundamental for inorganic LDI matrices. Compared with conventional organic matrices, vacancy-clustered MoO _x increases desorption and ionization efficiency by 3- to 27-fold and expands metabolite coverage by at least twofold. In-situ characterizations and calculations reveal that vacancy-clustered defect organization redirects post-excitation surface charge migration, promotes proton-coupled interfacial activation and lowers the energetic barrier for metabolite-ion release, establishing a charge-driven desorption and ionization basis for inorganic LDI matrices. Leveraging these advantages, this unified LDI-MS platform enables high-sensitivity cohort-scale serum metabolomics and high-resolution spatial tissue metabolomics in hepatocellular carcinoma. It reveals circulatory metabolic characteristics spatially associated with tumor regions, providing direct evidence of metabolic associations between blood and tumor tissue. These findings show vacancy-clustered engineering as a practical strategy for inorganic LDI matrices and provide an integrated platform for multidimensional disease metabolomics.

A global ground electronic state potential energy surface for the OH + NH ₃ reaction is constructed. The PES accurately describes not only the hydrogen abstraction channel, but also the NH ₂ OH formation channel.

Full-dimensional simulations reveal roaming as a general, nontraditional pathway. Its distinctive dynamics and energy redistribution significantly affect product branching and reaction rates, beyond the conventional minimum-energy-path paradigm.

Bimolecular nucleophilic substitution (S _N 2) and base-induced elimination (E2) reactions play crucial roles in chemistry. Here, we report a combined study of ion-molecule crossed-beam 3D velocity map imaging experiments and dynamics simulations on an accurate 39-dimensional potential energy surface for the Cl ⁻ + (CH ₃ ) ₃ CI reaction, allowing the most rigorous investigation of the atomistic dynamics. Good agreement between experimental and theoretical product angular and energy distributions is achieved, revealing that predominantly direct E2 reactions produce the majority of highly excited neutral products and slow ion product distributions. Moreover, we uncover a direct “flip-over” retention mechanism for the S _N 2 reaction, where substitution occurs via the direct flipping of the tert-butyl group, leading to retention of the tetrahedral carbon center. This mechanism manifests as a predominant forward-scattering feature in the product angular distribution and provides an important perspective on substitution dynamics in organic reactions.

The dissociative chemisorption of water on a Cu/Ni(111) bimetallic alloy surface was investigated using a combined neural-network potential energy surface and quantum dynamics approach. A full-dimensional (9D) PES was constructed and validated, enabling efficient seven-dimensional (7D) quantum wave packet calculations. Approximate 9D dissociation probabilities were obtained by site-averaging the 7D, site-specific results. The Cu monolayer is under 3.2% compressive strain, leading to a higher barrier height of 1.20 eV on Cu/Ni(111) than on pure Cu(111) (1.08 eV) and, consequently, to lower dissociation probabilities. The more reactive subsurface Ni atom induces a distinct site reactivity order (hcp > fcc > bridge > top). Strong mode specificity was observed, where vibrational excitations of the symmetric stretching, asymmetric stretching, and bending modes of H2O were found to be more efficacious than increasing the translational energy in promoting the reaction, with the asymmetric stretching mode providing the greatest enhancement and the bending mode the smallest. This mode-specific behavior aligns with earlier findings for water dissociation on pure Cu(111) and Ni(111) surfaces.

Quantum resonances exert a crucial impact on chemical reactivity, but experimental evidence has so far been restricted to transition-state or product-channel features. Here we provide the first direct evidence of van der Waals (vdW) resonances in the entrance channel of a neutral molecular reaction. Using fully quantum-state resolved crossed molecular beam scattering, we studied the benchmark F + H2(v = 0, j = 1) reaction over collision energies from 4.0 to 26.4 cm−1. A pronounced forward scattering peak of the HF(v′ = 2) product at 6.8 cm−1 reveals a resonance arising from quasi-bound states trapped in the entrance-channel vdW well, facilitated by centrifugal barriers. This signature is reproduced by quantum dynamical calculations on an open-shell diabatic potential energy surface, revealing partial wave resonances with total angular momentum (J) = 6.5–7.5 and demonstrating that spin-orbit coupling decisively shifts the energies of these quasi-bound states, shaping both the resonance position and scattering distribution. This combined experimental and theoretical study establishes a general quantum mechanism likely to influence a wide range of elementary reactions at low temperatures, including those relevant to interstellar chemistry and cold controlled systems.

Quantum interference between reaction pathways plays a crucial role in understanding the microscopic mechanisms of chemical reactions. The hydrogen exchange reaction, involving a well-characterized conical intersection, exhibits rich dynamics arising from interference between multiple reactive pathways. Here, we report high-resolution scattering measurements at a collision energy of 2.38 eV, which reveal pronounced sideways angular oscillations in the HD product distribution. Together with exact quantum theoretical calculations, these results provide unambiguous evidence of geometric phase-induced quantum interference in the H + D₂ reaction. Detailed analysis reveals that the observed sideways scattering oscillations, hallmarks of quantum interference, are strongly influenced by transient D–D bond elongation in D₂ reactants. This behavior, in contrast to the reaction with HD, highlights a pronounced isotopic effect and reflects the unique dynamic competition along the roaming insertion pathway. Collectively, these findings underscore the critical role of pathway interference and provide new mechanistic insights into how the isotopic effect modulated the geometric phase in an elementary chemical reaction.

Due to its potential applications in HF chemical lasers and its significance as a prototypical polyatomic reaction, the F + C₂H₆ reaction has long been a central topic in chemical kinetics and molecular dynamics. Although previous studies have reported both experimental and theoretical rate constants, discrepancies among these results persist. Moreover, the available experimental data do not cover the full temperature range, particularly at temperatures above room temperature, which are highly relevant to combustion and chemical laser applications. In this work, we report a new FI-NN potential energy surface (PES) developed at the gold-standard CCSD(T) level, which has been validated by its ability to reproduce HF rovibrational state distributions in close agreement with experimental results. Using this PES, we computed rate coefficients over the temperature range of 200-1100 K via direct ring-polymer molecular dynamics (RPMD). The calculated rates show good agreement with available experimental data in the low-temperature regime and extend reliable predictions to the high-temperature region relevant to combustion and chemical laser processes. These accurate RPMD rate coefficients can be combined with quasi-classical trajectory (QCT) calculations to yield reliable state-resolved dynamics and rate coefficients, thereby providing a consistent kinetic description across a broad temperature range.