Ionization Avalanching in Clusters Ignited by Extreme-Ultraviolet Driven Seed Electrons

Area of Science:

• Laser-induced dynamics
• Atomic and molecular physics
• Plasma science

Background:

• Tunnel ionization typically requires high laser intensities to initiate nanoplasma formation.
• Controlling ionization dynamics in clusters below the threshold is challenging.

Purpose of the Study:

• To investigate the ionization dynamics of argon clusters below the nanoplasma formation threshold.
• To demonstrate a method for controlling ionization and highly charged ion emission using a dual-pulse laser approach.

Main Methods:

• Experimental study of argon clusters exposed to ultrashort near-infrared (NIR) laser pulses.
• Utilizing an ultrashort extreme-ultraviolet (XUV) pulse to generate seed electrons prior to the NIR pulse.
• Employing molecular dynamics simulations to model and explain the observed phenomena.

Main Results:

• Emission of highly charged ions (up to Ar^{8+}) was achieved with high contrast by pre-seeding with XUV pulses.
• Simulations confirmed efficient heating via inverse bremsstrahlung and avalanche ionization.
• Resonant collective nanoplasma heating was predicted as a subsequent stage.

Conclusions:

• Controlled injection of seed electrons provides a precise method to initiate and control laser-driven nanoplasma dynamics.
• This technique offers new pathways for manipulating avalanching and heating in nanostructures and solids.
• Implications for fundamental and applied laser-matter science, including materials processing and particle acceleration.