Ekaterina I. Staroselskaya

Photoelectron angular distribution in two-pathway ionization of neon with femtosecond XUV pulses

Abstract We analyze the photoelectron angular distribution in two-pathway interference between nonresonant one-photon and resonant two-photon ionization of neon. We consider a bichromatic femtosecond XUV pulse whose fundamental frequency is tuned near the 2p53s atomic states of neon. The time-dependent Schrödinger equation is solved and the results are employed to compute the angular distribution and the associated anisotropy parameters at the main photoelectron line. We also employ a time-dependent perturbative approach, which allows obtaining information on the process for a large range of pulse parameters, including the steady-state case of continuous radiation, i.e., an infinitely long pulse. The results from the two methods are in relatively good agreement over the domain of applicability of perturbation theory. Graphical abstract

A variationally stable method in the problem of two-photon atomic ionization

A variationally stable method is analyzed; it is one of the rarely used approaches for calculating the amplitudes of nonlinear photoprocesses in the framework of perturbation theory. The convergence of the method is studied based on the example of atomic hydrogen and hydrogenlike ions. The method is used to calculate the angular distributions of photoelectrons for the first time.

Coherent control of the photoelectron angular distribution in photoionization of neon

Light-induced coherent control of the photoelectron angular distribution (PAD) in neon was recently achieved using the Free-Electron Laser (FEL) at FERMI [1]. This experimental tour de force promises a rich field of possibilities in the control of matter and has prompted new research in this exciting field. In order to gain a better understanding of these processes, we investigated two-pathway interferences in the ionization of neon induced by the fundamental and second harmonic of a femtosecond XUV pulse, i.e., the ω+2ω process. We consider the cases for which either (2p3s)P1 [2] or (2p4s)P1 are chosen as intermediate states to enhance the twophoton ionization probability. Douguet et al.: Photoelectron angular distribution in twoathway ionization of ne n with femtosecond XUV pulses 7

Photoelectron angular distribution in bichromatic atomic ionization

Theoretical aspects of photoelectron angular distributions are discussed with reference to bichromatic ionization by an FEL beam. Specifically, we consider an asymmetry in the angular distribution due to interference between the ionization paths from the fundamental and the second harmonic. The case of circularly polarized radiation is analyzed in detail in the vicinity of an intermediate resonance in the two-photon ionization paths. Similarities and differences to interference phenomena due to non-dipole effects are also discussed.