Tunneling Excitation to Resonant States in Helium as Main Source of Superponderomotive Photoelectrons in the Tunneling Regime

摘要: We present numerical solutions of the time-dependent Schr\"odinger equation in single-active-electron approximation and calculate wave functions for photoionization helium exposed to 800 nm light. Electron spectra show $\ensuremath{\sim}200$ peaks up 272 eV, due above-threshold ionization. The simulations confirm existence a wide, flat plateau electron spectrum backscattering, between 3 8 times ponderomotive energy. Electrons this range originate almost exclusively through resonance enhancement by quivering excited states, which turn are populated light-induced tunneling from ground state.