Angular Momentum Transfer between a Molecular System and a Continuous Circularly Polarized Light Field under the Born-Oppenheimer Framework

We demonstrate (both analytically and numerically) total angular momentum conservation for a molecular system subject to circularly polarized light (CPL) field moving along a single Born-Oppenheimer surface, where all of the angular momentum transfer is embodied in a Berry force. Moreover, we demonstrate that the model Hamiltonian proposed in [J. Chem. Phys. 150, 124101 (2019)] in fact corresponds physically to a homonuclear diatomic in a CPL field. Our results not only reveal an interesting microscopic mechanism for angular momentum transfer between a molecule and a radiation field, but they also provide new insight into the nature of novel semiclassical non-adiabatic dynamics methods that conserve the total angular momentum (including, e.g., phase-space surface-hopping methods).