Dark and bright autoionizing states in resonant high-order harmonic generation: Simulation via a one-dimensional helium model

We study the role of dark and bright autoionizing states (AISs) in photoionization high-order harmonic generation (HHG) using a one-dimensional helium model. This model allows numerical integration time-dependent Schr\"odinger equation beyond single-electron approximation, completely taking into account electronic correlation. find level structure system spatial distribution density for several states, including AIS. Studying HHG efficiency as function detuning from resonances with AISs, we enhancement lines. The shapes these lines are different corresponding Fano photoelectronic spectra, agreement experimental studies on helium. Moreover, simulate under conditions when fundamental frequency is close to even-order multiphoton resonance enhanced neighboring odd harmonics. details harmonics can be understood by temporal delay between nonresonant resonant XUV emissions; this defined AIS lifetime. Finally, our simulations show that AISs enhance similar extent.