Sub-barrier Coulomb effects on the interference pattern in tunneling-ionization photoelectron spectra

摘要

We use a quantum trajectory-based semiclassical method to account for Coulomb interaction betweennthe photoelectron and the parent ion in the classically forbidden sub-barrier region during strong-fieldntunneling-ionization processes. We show that—besides the well-known modification of the tunneling-ionizationnprobability—there is also an influence on the interference pattern in the photoelectron spectra. In thenlong-wavelength limit, the shift of the intracycle interference fringes caused by sub-barrier Coulomb effectsnin the laser polarization direction can be derived analytically. We compare our results with ab initio solutionsnof the time-dependent Schr¨odinger equation and find good agreement in the long-wavelength regime, whereasnthe standard strong-field approximation fails. We show that the nodal structure along low-order above-thresholdnionization rings is also affected by sub-barrier Coulomb effects.