Zijiang Yang

Polarized-light experiments are an important component of college physics laboratory teaching. However, their core concepts are relatively abstract, and traditional teaching methods often fail to present the underlying physical mechanisms in a dynamic and intuitive manner. In this study, a Matlab-based interactive digital resource was developed for the teaching of polarized-light experiments. The resource consists of three modules: polarization states, Malus' law, and Brewster's law. It dynamically visualizes the evolution of light polarization states, the variation of transmitted light intensity in Malus' law, and the changes in Brewster angle and reflectance in Brewster's law. These visualizations help students intuitively understand polarization states, Malus' law, and Brewster's law. In addition, students can independently adjust relevant parameters to observe physical phenomena and verify theoretical laws, thereby overcoming some limitations of traditional experiments and deepening their understanding of polarized-light principles. The proposed resource can serve as an effective auxiliary teaching tool and help improve students' learning efficiency.

Nonadiabatic dynamic study of the H + LiD(ν = 0, j = 0) → Li(2s) + HD reaction is carried out using the time-dependent wave packet method in a collision energy range of 1-80 cm^-1. The total integral cross section exhibits a partial wave resonance near 2 cm^-1, corresponding to the opening of the J = 5 partial wave. The nonadiabatic coupling effects inhibit the reactivity, especially for the low-vibrational states. The rotational excitation of products is affected by nonadiabatic coupling effects. The maximum accessible rotational state of the products is higher when nonadiabatic effects are included than when they are omitted. At low collision energies, the product angular distributions are influenced by the resonances. Nonadiabatic results reveal a more pronounced backward scattering of the products than adiabatic results. As collision energy increases, the stripping mechanism gradually becomes dominant, and both adiabatic and nonadiabatic results exhibit significant forward-scattering characteristics.

The collisions between Na atoms and H₂ molecules are of great significance in the field of chemical reaction dynamics, but the corresponding dynamics results of ground-state reactions have not been reported experimentally or theoretically. Herein, a global and high-precision potential energy surface (PES) of NaH₂ (1²A′) is constructed by the neural network model based on 21,873 high-level ab initio points. On the newly constructed PES, the quantum dynamics calculations on the Na(²S) + H₂(v₀ = 0, j₀ = 0) → NaH + H reaction are carried out using the time-dependent wave packet method to study the microscopic reaction mechanism at the state-to-state level. The calculated results show that the low-vibrational products are mainly formed by the dissociation of the triatomic complex; whereas, the direct reaction process dominates the generation of the products with high-vibrational states. The reaction generally follows the direct H-abstraction process, and there is also the short-lived complex-forming mechanism that occurs when the collision energy exceeds the reaction threshold slightly. The PES could be used to further study the stereodynamics effects of isotope substitution and rovibrational excitations on the title reaction, and the presented dynamics data would provide an important reference on the corresponding experimental research at a higher level.

Chemical reactions between Be⁺ ions and H₂ molecules have significance in the fields of ultracold chemistry and astrophysics, but the corresponding dynamics studies on the ground-state reaction have not been reported because of the lack of a global potential energy surface (PES). Herein, a globally accurate ground-state BeH₂⁺ PES is constructed using the neural network model based on 18,657 ab initio points calculated by the multi-reference configuration interaction method with the aug-cc-PVQZ basis set. On the newly constructed PES, the state-to-state quantum dynamics calculations of the Be⁺(²S) + H₂(v₀ = 0; j₀ = 0) and Be⁺(²S) + D₂(v₀ = 0; j₀ = 0) reactions are performed using the time-dependent wave packet method. The calculated results suggest that the two reactions are dominated by the complex-forming mechanism and the direct abstraction process at relatively low and high collision energies, respectively, and the isotope substitution has little effect on the reaction dynamics characteristics. The new PES can be used to further study the reaction dynamics of the BeH₂⁺ system, such as the effects of rovibrational excitations and alignment of reactant molecules, and the present dynamics data could provide an important reference for further experimental studies at a finer level.

The reactive collision between Ca and H2 molecules has attracted great interest experimentally due to the key role of the product CaH molecule in the field of astrophysics and cold molecules. However, quantum dynamics calculations for this system have not been reported due to the lack of a global potential energy surface (PES). Herein, a globally accurate PES of the ground-state CaH2 is developed by combining 11365 high-level ab initio points and permutation invariant polynomial neural network method. Based on the newly constructed PES, the state-to-state quantum dynamics calculations for the Ca­(1S) + H2 (v0 = 0, j0 = 0) → CaH + H reaction are carried out using the time-dependent wave packet method. The dynamic results reveal that the reaction follows the complex-forming mechanism near the reactive threshold, whereas both the indirect insertion mechanism and direct abstraction mechanism have effects at higher collision energies. The newly constructed PES can be used to further study the influence of isotope substitution, rovibrational excitation, and spatial orientation of reactant molecules on reaction dynamics.

The dynamic mechanisms and intramolecular isotope effects of the Be(¹S) + HD (v₀ = 2, j₀ = 0) → BeH/BeD + H/D reaction are studied at the state-to-state level using the time-dependent wave packet method on a high-quality potential energy surface. This reaction can proceed along the indirect pathway that features a barrier and a deep well or the smooth direct pathway. The reaction probabilities, total and state-resolved integral cross sections, and differential cross sections are analyzed in detail. The calculated dynamics results show that both of the products are mainly formed by the dissociation of a collinear HBeD intermediate when the collision energy is slightly larger than the threshold. As the collision energy increases, the BeH + D channel is dominated by the direct abstraction process, whereas the BeD + H channel mainly follows the complex-forming mechanism.

Fully converged nonadiabatic dynamics calculations of the D+ + H-2 -> H+ + HD reaction are performed at low temperatures using the time-dependent wave packet approach based on a set of precise 3 x 3 diabatic potential energy surfaces (PESs) ( Phys. Chem. Chem. Phys., 2021, 23, 7735-7747, DOI: 10.1039/D0CP04100A). The D+ + H-2 reaction is mediated by a dense manifold of resonances associated with the deep potential well on the ground-state PES. The calculated results show that the nonadiabatic coupling can affect the resonance positions, deviating from the expectation based solely on adiabatic considerations. Furthermore, significant forward-backward asymmetry in total differential cross sections (DCSs) is revealed, which is markedly influenced by nonadiabatic effects. The nonadiabatic effects not only affect the contribution of partial waves in the reaction but also make the interference patterns in the DCSs change significantly.

Coriolis coupling plays a crucial role in reactive scattering, but dynamics calculations including the complete Coriolis coupling significantly increase the difficulty of numerical evolution due to the corresponding expensive matrix processing. The coupled state approximation that completely ignores the off-diagonal Coriolis coupling saves computational cost significantly but its error is usually unacceptable. In this paper, an improved coupled state approximation inspired by recently published results [D. Yang, X. Hu, D. H. Zhang and D. Xie, J. Chem. Phys., 2018, 148, 084101.] of the inelastic scattering problem is extended to deal with the reactive scattering. The calculations using the time-dependent wave packet method reveal that the new method can accurately reproduce the rigorous results of the H + HD (j₀ < 3) → D + H₂ reaction and immensely improve the computational efficiency. Additionally, we extend the new method to the non-adiabatic Li(2p) + H₂ (v₀ = 0, j₀ = 0, 1) → H + LiH reaction, showcasing its advantages of low computational cost and high accuracy.

The LiNa₂ reactive system has recently received great attention in the experimental study of ultracold chemical reactions, but the corresponding theoretical calculations have not been carried out. Here, we report the first globally accurate ground-state LiNa₂ potential energy surface (PES) using a Gaussian process model based on only 1776 actively selected high-level ab initio training points. The constructed PES had high precision and strong generalization capability. On the new PES, the quantum dynamics calculations on the Li(²S) + Na₂(v = 0, j = 0) → LiNa + Na reaction were carried out in the 0.001–0.01 eV collision energy range using an improved time-dependent wave packet method. The calculated results indicate that this reaction is dominated by a complex-forming mechanism at low collision energies. The presented dynamics data provide guidance for experimental research, and the newly constructed PES could be further used for ultracold reaction dynamics calculations on this reactive system.