### Abstract

We describe an ab initio nonperturbative time-dependent R-matrix theory for ultrafast atomic processes. This theory enables investigations of the interaction of few-femtosecond and -attosecond pulse lasers with complex multielectron atoms and atomic ions. A derivation and analysis of the basic equations are given, which propagate the atomic wave function in the presence of the laser field forward in time in the internal and external R-matrix regions. To verify the accuracy of the approach, we investigate two-photon ionization of Ne irradiated by an intense laser pulse and compare current results with those obtained using the R-matrix Floquet method and an alternative time-dependent method. We also verify the capability of the current approach by applying it to the study of two-dimensional momentum distributions of electrons ejected from Ne due to irradiation by a sequence of 2 as light pulses in the presence of a 780 nm laser field.

Original language | English |
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Article number | 053411 |

Number of pages | 11 |

Journal | Physical Review A (Atomic, Molecular, and Optical Physics) |

Volume | 79 |

Issue number | 5 |

DOIs | |

Publication status | Published - 13 May 2009 |

### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics

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## Cite this

Lysaght, M. A., van der Hart, H. W., & Burke, P. G. (2009). Time-dependent R -matrix theory for ultrafast atomic processes.

*Physical Review A (Atomic, Molecular, and Optical Physics)*,*79*(5), [053411]. https://doi.org/10.1103/PhysRevA.79.053411