Modeling of clusters in a strong $248\text{‐}\mathrm{nm}$ laser field by a three-dimensional relativistic molecular dynamic model

A relativistic time-dependent three-dimensional particle simulation model has been developed to study the interaction of intense ultrashort KrF laser pulses with small Xe clusters. The trajectories of the electrons and ions are treated classically according to the relativistic equation of motion. The model has been applied to a different regime of ultrahigh intensities extending to . In particular, the behavior of the interaction with the clusters from intensities of to intensities sufficient for a transition to the so-called “collective oscillation model” has been explored. At peak intensities below , all electrons are removed from the cluster and form a plasma. It is found that the “collective oscillation model” commences at intensities in excess of , the range that can be reached in stable relativistic channels. At these high intensities, the magnetic field has a profound effect on the shape and trajectory of the electron cloud. Specifically, the electrons are accelerated to relativistic velocities with energies exceeding in the direction of laser propagation and the magnetic field distorts the shape of the electron cloud to give the form of a pancake.

Figure 1

Positions of the test particles in the $XY$ plane at different times. “X” is the parallel to the laser field and “$+Y$” is the direction of propagation. The laser and cluster parameters are $I_0={10}^{17}\mathrm{W}∕{\mathrm{cm}}^2$, $\lambda =248\mathrm{nm}$, $R_0=20\mathrm{\AA }$, $N=393\text{atoms}∕\text{cluster}$, and $Z=13$. The number of test particles is $\sim {10}^3$.

Figure 2

Number of inner electrons (dashed line), outer electrons (dotted line), and total number of electrons (solid line) (a), kinetic, potential, and total energy (b), and mean electron and ion energy (c) vs time. The conditions are the same as in Fig. 1.

Figure 3

EEDF at different times. The conditions are the same as in Fig. 1.

Figure 4

Positions of the test particles in the $XY$ plane at different times. The laser and cluster parameters are $I_0={10}^{19}\mathrm{W}∕{\mathrm{cm}}^2$, $\lambda =248\mathrm{nm}$, $R_0=20\mathrm{\AA }$, $N=393\text{atoms}∕\text{cluster}$, and $Z=27$.

Figure 5

Kinetic, potential, and total energy (a) and mean electron and ion energy (b) vs time. The conditions are the same as in Fig. 4.

Figure 6

EEDF at different times. The conditions are the same as in Fig. 4.

Figure 7

Positions of the test particles in the $XY$ plane at different times. The laser and cluster parameters are $I_0={10}^{21}\mathrm{W}∕{\mathrm{cm}}^2$, $\lambda =248\mathrm{nm}$, $R_0=20\mathrm{\AA }$, $N=393\text{atoms}∕\text{cluster}$, and $Z=45$.

Figure 8

(Color online) Positions of the test particles at different times. The conditions are the same as in Fig. 7.

Figure 9

Electron excursion (a), kinetic, potential, and total energy (b), and mean electron and ion energy (c) vs time. The conditions are the same as in Fig. 7.

Figure 10

Normalized cluster size $R∕R_0$ vs time for peak laser intensities $I_0={10}^{17}$, ${10}^{19}$, ${10}^{21}\mathrm{W}∕{\mathrm{cm}}^2$.