On the angular dependence of the photoemission time delay in helium

Abstract

We investigate an angular dependence of the photoemission time delay in helium as measured by the RABBITT (Reconstruction of Attosecond Beating By Interference of Two-photon Transitions) technique. The measured time delay ${\tau }_a={\tau }_W+{\tau }_{cc}$ contains two distinct components: the Wigner time delay ${\tau }_W$ and the continuum-continuum CC) correction ${\tau }_{cc}$. In the case of helium with only one $1s\to Ep$ photoemission channel, the Wigner time delay ${\tau }_W$ does not depend on the photoelectron detection angle relative to the polarization vector. However, the CC correction ${\tau }_{cc}$ shows a noticeable angular dependence. We illustrate these findings by performing two sets of calculations. In the first set, we solve the time-dependent Schrödinger equation for the helium atom ionized by an attosecond pulse train and probed by an IR pulse. In the second approach, we employ the lowest order perturbation theory which describes absorption of the XUV and IR photons. Both calculations produce close results in a fair agreement with experiment.

References in corpus (6)

• Probing single-photon ionization on the attosecond time scale
• Theory of attosecond delays in laser-assisted photoionization
• Attosecond pulse shaping around a Cooper minimum
• Parameterized optimized effective potential for the ground state of the atoms He through Xe
• Angle-resolved time delay in photoemission
• Angle-resolved time delay in photoemission of neon

Cited by in corpus (1)

• Angle-resolved RABBIT: theory and numerics