Plasmon-enhanced electron acceleration in intense laser metal-cluster interactions.

Area of Science:

• Atomic and Molecular Physics
• Condensed Matter Physics
• Laser Physics

Background:

• Understanding electron emission from nanoclusters is crucial for applications in ultrafast electron sources and material science.
• Plasmon excitation in metal nanoclusters significantly influences their electronic properties and response to external fields.

Purpose of the Study:

• To investigate the energy and angular-resolved electron emission from silver nanoclusters under dual laser pulse excitation.
• To elucidate the underlying mechanism responsible for enhanced and anisotropic electron emission.

Main Methods:

• Experimental measurement of energy and angular-resolved electron emission from silver clusters (N ≈ 500–2000).
• Utilizing dual laser pulses with moderate intensity (I ≈ 10^13–10^14 W/cm^2).
• Employing semiclassical simulations to model electron dynamics within the cluster.

Main Results:

• Observed enhanced electron emission along the laser polarization axis when the second pulse resonantly excites plasmons.
• Demonstrated a strong increase in the asymmetry of the electron spectrum with increasing electron energy.
• Identified a mechanism involving electrons leaving, returning, and traversing the cluster, accelerated by the plasmon field.

Conclusions:

• The study reveals a novel mechanism for energetic electron emission from silver nanoclusters driven by resonant plasmon excitation.
• Electrons experiencing specific conditions of return and traversal within the cluster are preferentially accelerated and emitted along the laser polarization axis.
• This anisotropic emission in subcycle bursts offers potential for developing advanced electron sources.