Electron-ion interaction effects in attosecond time-resolved photoelectron spectra

Abstract

Photoionization by attosecond extreme ultraviolet (xuv) pulses into the laser-dressed continuum of the ionized atom is commonly described in strong-field approximation, neglecting the Coulomb interaction between the emitted photoelectron (PE) and the residual ion. By solving the time-dependent Schrödinger equation, we identify a temporal shift δτ in streaked PE spectra, which becomes significant at low PE energies. Within an eikonal approximation, we trace this shift to the combined action of Coulomb and laser forces on the released PE, suggesting the experimental and theoretical scrutiny of their coupling in streaked PE spectra. Further, we examined the effect of initial state polarization by the laser pulse on the xuv streaked spectrum.

Attosecond delays in laser-assisted photodetachment from closed-shell negative ions

“…Relative time delays have also been measured between different atomic species [12][13][14], between single and double ionization [15], between different angles of photoemission [16] and between the ion ground state and shake-up states [17]. In the case of atomic photoionization it has been established that the measured atomic delay τ A can be separated into a Wigner-like delay [18][19][20], τ W , here associated with the one-photon XUV ionization process, and a contribution from the interaction with the laser and long-range ionic field, τ CC , called the continuum-continuum delay (or Coulomb-laser coupling delay) [21][22][23]. The τ CC term is "universal" in the sense that it depends only on the kinetic energy of the photoelectron, the photon energy of the laser field and the charge of the remaining ion (Z = 1 for neutral targets).…”

Initial-state, mean-free-path, and skin-depth dependence of attosecond time-resolved IR-streaked XUV photoemission from single-crystalline magnesium

“…The dipole-length-gauge interaction emphasizes large distances [30]. It is thus appropriate for large distances z > 0 on the vacuum side of the metal-vacuum interface where our approximate representation of the true final-state wave function in terms of a "Volkov" wave function (see below) is more accurate than for small distances [31]. Our use of the dipole-length gauge is furthermore motivated by length-gauge SFA calculations for atomic ionization processes matching exact numerical calculations [32].…”

Probing dielectric-response effects with attosecond time-resolved streaked photoelectron spectroscopy of metal surfaces

“…We describe the release and propagation of the PE wave packet δψ n (z,t) from occupied substrate states ψ n (z,t) by solving the TDSE [11],…”

“…Essential for the correct reproduction of this shift within quantum mechanical models [10,11] is the proper inclusion of (i) the photoelectron's (PE's) phase evolution in the IR laser field during streaked emission, (ii) the attenuation of the IR pulse inside the solid (skin effect), and (iii) PE transport effects in the solid [12,13]. The release and subsequent motion of the PE in and in front of a solid dielectric medium provoke collective electron excitations in the solid.…”