Effect of low-energy electron interference on strong-field molecular ionization

By using a three-dimensional time-dependent Schrödinger equation, we calculate alignment-dependent ionization of model diatomic molecules subjected to an intense laser field with different internuclear distances. It is found that the ionization probability shows oscillatory behavior with respect to the angle between the laser polarization direction and the molecular axis for large internuclear distances. Comparing with the results obtained by Ammosov–Delone–Krainov (ADK) theory and $S$-matrix theory, the intriguing phenomenon can be attributed to the two-center interference effect of low-energy photoelectrons. Furthermore, it is shown that ADK theory is not applicable for the investigation of molecular ionization for large internuclear distances.

Figure 1

(a) Normalized ionization probability as a function of alignment angle $\beta$ with increasing internuclear separations obtained by TDSE (see text). (b)–(d) Normalized probabilities of electron spectra in different ranges versus $\beta$ for $R=10$, 20, and 30 a.u., respectively.

Figure 2

(a), (b) Ionization probability versus $\beta$ calculated from ADK theory. (c) Normalized ionization probability as a function of alignment angle $\beta$ for different internuclear distances obtained by SFA (see text). (d)–(f) Normalized probabilities of electron spectra in different ranges calculated by DSFA with increasing $\beta$ for $R=10$, 20, and 30 a.u., respectively.

Figure 3

(a)–(c) ${cos}^2(\mathbf{P}·\mathbf{R}/2)$ as a function of momentum of the emitted electron $P$ and angle $\theta$ between $\mathbf{P}$ and the internuclear axis with increasing $R$. (d) Normalized integral versus alignment angle $\beta$ with increasing $R$, obtained by the integral in a small solid angle (see text).