Interference in above-threshold-ionization electron distributions from molecules

We present quantum-mechanical studies on above-threshold ionization of molecular ions in two and three dimensions. The momentum distributions show signatures of interfering emissions from the molecular centers. These structures deviate from a simple double-slit model that ignores the electron-ion interaction, but they are reproduced by an eikonal model. Such distortions of the interference pattern are partly responsible for the absence of clear interference patterns in the angle-integrated electron energy spectra.

Figure 1

Momentum distributions for $\mathrm{H}{{}_2}^{+}$ at the internuclear distances $R=20\hspace{0.5em}$a.u. aligned perpendicular tothe laser field (logarithmic color scale). (a–e) Time-dependent distributions in the interaction region at different times $t$, as indicated.The laser field is turned off at $t=16T$. (f) Asymptotic photoelectron distribution.

Figure 2

Asymptotic momentum distributions ${\sigma }_{\mathrm{AS}}$ for $\mathrm{H}{{}_2}^{+}$ at $R=20\hspace{0.5em}$a.u. with (a) perpendicular alignment and (b) parallel alignment of the molecular axis to the laser field. The red lines indicate the minima predicted by the eikonal model, Eq. (7).

Figure 3

Asymptotic momentum distributions ${\sigma }_{\mathrm{AS}}$ for ${\mathrm{H}}_3{}^{2+}$. (a) Perpendicular alignment with the nuclei positioned at $R_1=(-10,0)$, $R_2=(0,0)$, and $R_3=(10,0)$. (b) Parallel alignment with $R_1=(0,-10)$, $R_2=(0,0)$, and $R_3=(0,10)$.The red straight, green dashed, and blue dotted lines are contour lines at the values 0.96, 0.93, and 0.92, respectively, of the surface given by the three-center eikonal model, Eq. (8), which yields values between 0.9 and 1.1.

Figure 4

Energy spectra obtained from Fig. 2 by integration over emission angle. (a) Spectrum for perpendicular alignment. (b) Spectrum for parallel alignment. (c) Ratio of parallel to perpendicular spectrums. The red lines are the positions of the minima predicted by $E_n=\pi {}^2(2n+1){}^2/(2R^2)$.

Figure 5

Asymptotic momentum distributions ${\sigma }_{\mathrm{AS}}$ for $\mathrm{H}{{}_2}^{+}$ perpendicular to the laser field as in Fig. 2, obtained as 2D cuts from the 3D calculation (logarithmic color scale). Also shown is the molecule-field geometry.