Interference substructure of above-threshold ionization peaks in the stabilization regime

The photoelectron spectra produced in the photodetachment of ${\mathrm{H}}^{-}$ (treated in the single-active-electron approximation) by strong high-frequency laser pulses with adequately chosen laser parameters in the stabilization regime are theoretically studied for elliptic polarization over an extended parameter range. An oscillating substructure in the above-threshold ionization peaks is observed, which confirms similar findings in the one-dimensional (1D) [K. Toyota et al., Phys. Rev. A 76, 043418 (2007)] and 3D calculations for linear polarization [O. I. Tolstikhin, Phys. Rev. A 77, 032712 (2008)]. The mechanism is an interference between the photoelectron wave packets created in the rising and falling parts of the pulse which is specific to the stabilization regime. We thus conclude that this interference substructure is robust for any polarization and over a wide range of the laser parameters, and hence should be observable experimentally.

Figure 1

(Color online) The partial wave and total photoelectron spectra for the reference laser pulse with the parameters $\epsilon =1$, $F_0=0.5$, $\omega =\pi ∕10$, and $T=600$. The multiphoton absorption energies $E_0+n\omega$ are shown by arrows. Note that the total spectrum is multiplied by 10 to separate it from the other curves.

Figure 2

(Color online) Momentum distribution of the photodetached electron in the $xy$ plane for the same (circularly polarized in the $xz$ plane) pulse as in Fig. 1.

Figure 3

(Color online) The first ATI peak for pulses with $\epsilon =1$, $\omega =\pi ∕10$, and $T=600$ and three values of the field amplitude $F_0=0.1$, 0.3, and 0.5.

Figure 4

(Color online) The first ATI peak for pulses with $\epsilon =1$, $F_0=0.5$, and $\omega =\pi ∕10$ and four values of the duration of the pulse $T=200$, 400, 600, and 800.

Figure 5

(Color online) The first ATI peak for pulses with $F_0=0.5$, $\omega =\pi ∕10$, and $T=600$ with linear $(\epsilon =0)$, intermediate elliptic $(\epsilon =0.5)$, and circular $(\epsilon =1)$ polarizations.

Figure 6

(Color online) The first ATI peak for linear polarization (LP) along the $z$ axis and in the case where the polarization axis is adiabatically rotated (AR) from $z$ to $x$ near the center of the pulse in order to suppress the interference (see text). The laser parameters are $F_0=0.5$, $\omega =\pi ∕10$, and $T=600$.

Figure 7

(Color online) (a) Energy (solid line) and one-photon decay width (dashed line) of the initial dressed state as functions of the excursion amplitude $\alpha =F_0∕{\omega }^2$ for $\omega =\pi ∕5$. (b) Same as in (a), but as functions of time recalculated using Eq. (18) for the laser pulse with $F_0=1.2$, $\omega =\pi ∕5$, and $T=2000$. The maximum value of $\alpha \left(t\right)$ for this pulse is shown by the vertical dotted line in the upper panel.

Figure 8

(Color online) The first ATI peak for a circularly polarized laser pulse with $F_0=1.2$, $\omega =\pi ∕5$, and $T=2000$. The HFFT results are obtained from Eq. (22).