On the Generation of Multiply Charged Argon Ions in Nanosecond Laser Field Ionization of Argon

TL;DR

This paper critiques a recent evaporation model explaining multiply charged argon ions in laser-irradiated clusters, arguing that plasma dynamics better describe the observed phenomena.

Contribution

It challenges the evaporation model by demonstrating that plasma behavior is more appropriate for explaining cluster explosion and ionization dynamics.

Findings

The evaporation model has intrinsic inconsistencies.

Plasma behavior better explains cluster heating and explosion.

Experimental results align with plasma-based explanations.

Abstract

Zhang and coworkers have recently reported results of experiments involving irradiation of argon clusters doped with bromofluorene chromophores by nanosecond-long pulses of 532 nm laser light. Multiply-charged ions of atomic argon (charge states, n, up to 7) and carbon (charge states up to 4) are observed which are sought to be rationalised using an evaporation model. The distinguishing facet of exploding clusters being progenitors of energetic ions and electrons constitutes the key driver for contemporary research in laser-cluster interactions; it is, therefore, important to point out inconsistencies that are intrinsic to the model of Zhang and coworkers. In light of similar reports already in the literature, we show that their model is of limited utility in describing the dynamics that govern how fast, multiply-charged atomic ions result from laser irradiation of gas-phase clusters. We posit that it is plasma behaviour that underpins cluster heating and cluster explosion dynamics.