Probing Electronic Motion and Core Potential by Coulomb-reshaped Terahertz Radiation

The nature of electronic motion and structural information of atoms and molecules is encoded into strong field induced radiations ranging from terahertz (THz) to extreme ultraviolet wavelength. The dependence of THz yields in bichomatic laser fields on ellipticity and interpulse time delay were experimentally measured, and the trajectory-based calculations straightforwardly establish the link between the THz emission and the motion of photoelectron wave packet under the influence of the Coulomb potential. The asymmetry of the photoelectron wave packet modified by the Coulomb potential imprints itself on the polarization direction of the THz electric fields. By filtering out the rapidly-varying dynamics of the propagating wave packet while retaining the slowly-varying dynamics, the Coulomb potential of the generating medium is retrieved from the Coulomb-reshaped THz radiation. Our work opens a path towards all-optical THz detection of electronic and structural dynamics, which might also allow to resolve the photo-excited dynamics in condensed phase systems.