Numerical simulation of THz-wave-assisted electron diffraction for ultrafast molecular imaging

A scheme for achieving high temporal resolution in gas electron diffraction is proposed, in which time-dependent electron diffraction patterns can be obtained from energy-resolved angular distributions of electrons scattered by molecules in dynamical processes under the presence of a single-cycle THz-wave pulse. Derived formulae of the differential cross section and numerical simulations of electron signals scattered by Ar atoms and $\mathrm{C}{\mathrm{l}}_2$ molecules show that the temporal resolution of the proposed method can be $<10\mathrm{fs}$ in the pump-probe measurement without scanning the time delay.

Figure 1

(a) THz pulse in the present simulation. Black solid line: Electric field. Red solid line: Vector potential. (b) Signal distribution of electrons scattered by Ar atoms. (c) Energy spectrum of scattered electrons.

Figure 2

(a) Schematic of the scattering configuration. (b, Top panel) Black thick solid line: The initially given temporal dependence of the internuclear distance ($R$) of the dissociating $\mathrm{C}{\mathrm{l}}_2$ molecule. Green thin solid line: The time-dependent internuclear distance retrieved from $I_{\mathrm{pos}}(s_{\parallel },t_{\mathrm{c}})$ shown in Fig. 3. (b, Bottom panel) Red solid line: The deviations of the retrieved internuclear distance from the initially given internuclear distance.

Figure 3

(a, b) Signal distributions of electrons scattered by rigid and dissociating $\mathrm{C}{\mathrm{l}}_2$ molecules, respectively. (c, d) Signal distributions of electrons scattered by rigid and dissociating $\mathrm{C}{\mathrm{l}}_2$ molecules, respectively, as a function of the momentum transfer and the absolute value of the collision time. (e) Signal distribution of electrons scattered by dissociating $\mathrm{C}{\mathrm{l}}_2$ molecules as a function of the momentum transfer and the collision time. (f) The temporal resolutions of the collision time as a function of $t_{\mathrm{c}}$ by assuming $s_{\parallel }=5.0\AA {}^{-1},\delta (\mathrm{\Delta }E)=0.2\mathrm{eV},\delta s_{\parallel }/s_{\parallel }=2\%$, and $\delta A/A=3\%$. The color scales for (b)–(e) are the same as that for (a).