Fig. 3
From: Nanoplasmonic electron acceleration by attosecond-controlled forward rescattering in silver clusters
Two-color nanoaccelerator model. a Schematics of scale-matched forward rescattering at a polarized sphere with potential V(x, t) = Vpol(x)p(t), where Vpol(x) is the static polarization potential (black curve) for unit dipole moment with amplitude V0. b Evolution of the two-color dipole moment p(t) (dashed curve) for a relative amplitude γpol = 1/8 and corresponding dipole acceleration \(\dot p\left( t \right)\) (solid curve). c Resulting gain map \(\frac{\partial }{{\partial t}}V = {V_{{\rm{pol}}}}\left( x \right)\dot p\left( t \right)\) with pronounced high-gain points (orange). Electron drift trajectories x(t) = (t − ttrans)vd for optimal passages in up (red) and down (blue) direction for drift velocity vd = 1.5vhct and relative dipole phase φpol = 0. Corresponding transit times ttrans are indicated as vertical dotted lines. Here vhct is the half cycle transit velocity (see text). d Transit time-dependent gain in the perturbative limit \({\rm{\Delta }}{E_{{\rm{sp}}}}\left( {{t_{{\rm{trans}}}}} \right) = {\int} {\kern 1pt} \frac{\partial }{{\partial t}}{V_{{\rm{pol}}}}\left( {x\left( t \right),t} \right){\kern 1pt} {\rm{d}}t\) for upward and downward electrons. The respective peak values (circular symbols) define the optimal trajectories. e Optimal gain for upward electrons vs. relative dipole phase φpol for selected drift velocities vd
