## Abstract

We study resonant two-photon ionization of helium atoms via the 1s3p, 1s4p and 1s5p^{1}P_{1} states using the 15^{th} harmonic of a titanium-sapphire laser for the excitation and a weak fraction of the laser field for the ionization. The phase of the photoelectron wavepackets is measured by an attosecond interferometric technique, using the 17^{th} harmonic. We perform experiments with angular resolution using a velocity map imaging spectrometer and with high energy resolution using a magnetic bottle electron spectrometer. Our results are compared to calculations using the two-photon random phase approximation with exchange to account for electron correlation effects. We give an interpretation for the multiple π-rad phase jumps observed, both at and away from resonance, as well as their dependence on the emission angle.

Original language | English |
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Article number | 964586 |

Journal | Frontiers in Physics |

Volume | 10 |

DOIs | |

Publication status | Published - 2022 Oct |

## Subject classification (UKÄ)

- Atom and Molecular Physics and Optics

## Keywords

- attosecond
- attosecond dynamics
- photoelectron interferometry
- photoionization
- photoionization dynamics