Observing a Berry curvature effect in ${\mathrm{CH}}_2\mathrm{OH}$ photodissociation via molecular dynamics simulations

The Berry curvature of molecular electronic wave function serves as an electron-spin-dependent effective magnetic field, which results in an effective magnetic force that can lead to electron-spin-dependent molecular dynamics. We propose an experimental scheme to observe this Berry curvature effect in molecular dynamics. We show that in ${\mathrm{CH}}_2\mathrm{OH}$ photodissociation process, the dissociation rates are different for molecules with opposite electronic spin directions, and the evolution of the electronic density of molecules with opposite spins can be observed with ultrafast x-ray diffraction using free electron lasers, which demonstrates the modified nuclear motion due to the electron-spin-dependent effective magnetic force. Our work paves the way to the direct observation of the Berry curvature effect in molecular systems and chemical reactions, and the Berry curvature effect has profound and wide applications in various areas of physics and chemistry.