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We theoretically study the pulse-width dependence of the photoelectronangular distribution (PAD) from the resonance-enhanced two-photon singleionization of He by femtosecond ($\lesssim 20$ fs) extreme-ultraviolet pulses,based on the time-dependent perturbation theory and simulations with the fulltime-dependent Schr\"odinger equation. In particular, we focus on thecompetition between resonant and nonresonant ionization paths, which leads tothe relative phase $\delta$ between the $S$ and $D$ wave packets distinct fromthe corresponding scattering phase shift difference. When the spectrallybroadened pulse is resonant with an excited level, the competition varies withpulse width, and, therefore, $\delta$ and the PAD also change with it. On theother hand, when the Rydberg manifold is excited, $\delta$ and the PAD do notmuch vary with the pulse width, except for the very short pulse regime.

Competition of resonant and nonresonant paths in resonance-enhanced two-photon single ionization of He by an ultrashort extreme-ultraviolet pulse