On the importance of field driven single particle processes in short pulse absorption of clusters

Soubhik Sarkar,M Anand,M Krishnamurthy,M Praveen Kumar,R Gopal

doi:10.1038/s41598-019-51385-5

Soubhik Sarkar, M Anand + Show 3 more

Open Access

https://doi.org/10.1038/s41598-019-51385-5

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Journal: Scientific Reports	Publication Date: Oct 22, 2019
Citations: 1	License type: open-access

Affiliation: Tata Institute of Fundamental Research

Abstract

Nano-clusters are acclaimed to be very efficient absorbers of intense femto second light due to dominant collective mechanisms. Enhanced near 100% absorption due to collective linear plasma resonance compared to a small fraction of absorption by unclustered gas was an important drive in nano-plasma studies. Contrary to such perception, we show that if the pulse duration is (<100 fs), absorption is same irrespective of whether the systems are condensed to large clusters or not. So long as there are same number of similar ionizable systems in the focal volume, absorption is the same and such absorption can be accounted for by single particle response to the field and collisional ionization of atoms. Short pulse absorption by the single particle response can be comparable to the linear plasma resonance absorption for smaller clusters.

Highlights

Nano-clusters are acclaimed to be very efficient absorbers of intense femto second light due to dominant collective mechanisms
Current understanding of the interaction of intense laser pulse with clusters based on many important studies in this field can be summarised into the following steps: (a) Intense laser pulse ionizes atoms by field ionization (b) Electrons released from atoms are driven by the laser field and contribute to collisional ionization. (c) Increase in electron density leads to formation of a plasma and collective absorption mechanisms like linear plasma resonance begins to enhance absorption of light. (d) Cluster expands/explodes both under hydrodynamic[13] or Coulomb[14,15] pressure releasing high energy ions and electrons
The short pulse absorption is dominated by the single particle response which itself can be as large as that due to linear plasma resonance

Summary

Introduction

Nano-clusters are acclaimed to be very efficient absorbers of intense femto second light due to dominant collective mechanisms. Is absorption by an enhanced local field, a result of collective mechanism of the nanoplasma, the only way of large energy deposition in laser cluster interactions?

Results

Conclusion