Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation study

Abstract

Linear resonance (LR) absorption of an intense 800~nm laser light in a nano-cluster requires a long laser pulse > 100~fs when Mie-plasma frequency ($\omegaMie$) of electrons in the expanding cluster matches the laser frequency~($\omega$). For a short duration of the pulse the condition for LR is not satisfied. In this case, it was shown by a model and particle-in-cell (PIC) simulations [Phys. Rev. Lett. 96, 123401 (2006)] that electrons absorb laser energy by anharmonic resonance (AHR) when the position-dependent frequency $\Omega [r(t)]$ of an electron in the self-consistent anharmonic potential of the cluster satisfies $\Omega [r(t)]=\omega$. However, AHR remains to be a debate and still obscure in multi-particle plasma simulations. Here, we identify AHR mechanism in a laser driven cluster using molecular dynamics (MD) simulations. By analyzing the trajectory of each MD electron and extracting its $\Omega [r(t)]$ in the self-generated anharmonic plasma potential it is found that electron is outer ionized {\em only} when AHR is met. An anharmonic oscillator model, introduced here, brings out most of the features of MD electrons while passing the AHR. Thus, we not only bridge the gap between PIC simulations, analytical models and MD calculations for the first time but also unequivocally prove that AHR processes is a universal dominant collisionless mechanism of absorption in the short pulse regime or in the early time of longer pulses in clusters.

References in corpus (11)

• Laser-driven nonlinear cluster dynamics
• Ionization of clusters in intense laser pulses through collective electron dynamics
• Asymmetric emission of high energy electrons in the two-dimensional hydrodynamic expansion of large xenon clusters irradiated by intense laser fields
• Nonlinear resonance absorption in laser-cluster interaction
• Intense high contrast femtosecond K-shell x-ray source from laser-driven Ar clusters
• Ionization heating in rare-gas clusters under intense XUV laser pulses
• Anisotropic "charge-flipping" acceleration of highly charged ions from $(N_2{)}_n$ clusters in strong optical fields
• Harmonic emission from cluster nanoplasmas subject to intense short laser pulses
• Dynamical ionization ignition of clusters in intense and short laser pulses
• Collisionless energy absorption in the short-pulse intense laser-cluster interaction
• Collisionless absorption, hot electron generation, and energy scaling in intense laser-target interaction

Cited by in corpus (2)

• Temporal Feedback Control of High-Intensity Laser Pulses to Optimize Ultrafast Heating of Atomic Clusters
• Dynamical resonance shift and unification of resonances in short-pulse laser cluster interaction