Rethinking electron-molecule scattering simulations

When an electron collides with a molecule, the electron can bounce off every which way. Predicting that scattering depends on the target molecular orbitals, a forecast of where, and in what state, the molecule’s electrons are likely to be when hit. Despite the scattering process’s importance for understanding plasma and chemical evolution, and for assessing the structural and dynamic properties of fundamental particles, theoretical and computational models still don’t align tightly with experimental results.

Fang et al. described a new, optimized way to predict target molecular orbitals that uses machine learning to help number and weight each possible electron state, rather than take an average, as is standard. The method yielded a strong match between predictions and experimental results for collisions with carbon monoxide molecules.

“Molecular target orbitals are not only useful for simulating electron-molecular scattering,” said author He Su. “They can be used to simulate processes like positron scattering, photoionization, and atom-diatom collision.”

The researchers first attempted to improve the accuracy of scattering results using the standard method of electronic state averages, but found limited improvements from changing parameters. So, they used machine learning to explore how many electron states were physically possible, then assigned weights to each, to describe the target molecular electronic wavefunctions. Thousands of scattering tests with the carbon monoxide molecule showed the state-weight method was highly accurate.

The team also discovered that the dipole moment and excitation energy of the carbon monoxide molecule had strong influences on its elastic and inelastic scattering patterns. In addition to its role as a test system, carbon monoxide is relevant for its presence in Mars’ and Venus’ atmospheres.

In the future, the researchers hope to develop a global optimization method, then apply it to more complex, polyatomic molecules.

Source: “Electron scattering on carbon monoxide: An optimization of target molecular orbitals,” by Fan Fang, He Su, Jonathan Tennyson, Qunchao Fan, Zhixiang Fan, Hong Zhang, and Xinlu Cheng, Journal of Chemical Physics (2026). The article can be accessed at https://doi.org/10.1063/5.0307607 .