Violation of centrosymmetry in time-resolved ultrafast-electron diffraction from vibrating oriented diatomic molecules

Violation of centrosymmetry (VOC) in time-resolved diffraction patterns has been predicted in ultrafast-electron and x-ray diffraction from electronic and molecular motions. Extending from our x-ray studies, we theoretically investigate the VOC in time-resolved ultrafast-electron diffraction from rovibrational motion of oriented diatomic molecules lithium hydride and hydrogen. We simulate and compare the electron and x-ray diffraction images, especially focused on the differences in the VOC and molecular interference fringes. In addition, using Newton diagrams, we provide an intuitive semiclassical interpretation to explain how the VOC is arisen from and related to the particles' motion and why is there an anticorrelation between the VOC and molecular interference fringes.