1,943 research outputs found
Analytical approximations for the higher energy structure in strong field ionization with inhomogeneous electric fields
Recently, the emergence of a higher energy structure (HES) due to a spatial
inhomogeneity in the laser electric field, as is typically found close to a
nano tip, was reported in Phys.~Rev. Letter {\bf 119}, 053204 (2017). For
practical applications, such as the characterization of near-fields or the
creation of localized sources of monoenergetic electron beams with tunable
energies, further insight into the nature of this higher energy structure is
needed. Here, we give a closed form analytical approximation to describe the
movement of the electron in the inhomogeneous electric field. In particular, we
derive a simple scaling law for the location of the HES peak and give a scheme
to analytically tune the width of the peak, both of which will prove useful in
optimizing the nanostructure size or geometry for creating the HES in
experimental settings
Intensity dependence of Rydberg states
We investigate numerically and analytically the intensity dependence of the
fraction of electrons that end up in a Rydberg state after strong-field
ionization with linearly polarized light. We find that including the intensity
dependent distribution of ionization times and non-adiabatic effects leads to a
better understanding of experimental results. Furthermore, we observe using
Classical Trajectory Monte Carlo simulations that the intensity dependence of
the Rydberg yield changes with wavelength and that the previously observed
power-law dependence breaks down at longer wavelengths. Our work suggests that
Rydberg yield measurements can be used as an independent test for
non-adiabaticity in strong field ionization
Controlling the quantum number distribution and yield of Rydberg states via the duration of the laser pulse
We show that the distribution of quantum numbers of Rydberg states does not
only depend on the field strength and wavelength of the laser which the atom is
exposed to, but that it also changes significantly with the duration of the
laser pulse. We provide an intuitive explanation for the underlying mechanism
and derive a scaling law for the position of the peak in the quantum number
distribution on the pulse duration. The new analytic description for the
electron's movement in the superposed laser and Coulomb field (applied in the
study of quantum numbers) is then used to explain the decrease of the Rydberg
yield with longer pulse durations. This description stands in contrast to the
concepts that explained the decrease so far and also reveals that
approximations which neglect Coulomb effects during propagation are not
sufficient in cases such as this.Comment: 8 pages, 8 figure
Instantaneous ionization rate as a functional derivative
We describe an approach defining instantaneous ionization rate (IIR) as a
functional derivative of the total ionization probability. The definition is
based on physical quantities which are directly measurable, such as the total
ionization probability and the waveform of the pulse. The definition is,
therefore, unambiguous and does not suffer from gauge non-invariance. We
compute IIR by solving numerically the time-dependent Schrodinger equation for
the hydrogen atom in a strong laser field. We find that the IIR lags behind the
electric field, but this lag is entirely due to the long tail effect of the
Coulomb field. In agreement with the previous results using attoclock
methodology, therefore, the IIR we define does not show measurable delay in
strong field tunnel ionization
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