Ionisation of Nanoclusters at Relativistic Laser Intensities

Abstract

Nanoclusters exposed to intense ultrashort pulses have attracted immense attention due to higher absorption and high charge state ion emission. Insofar, most of the studies in Coulomb explosion of clusters have been at non-relativistic laser intensities. The question of how the ionisation of the clusters change at relativistic intensities $({>}2\times 10^{18}$ Wcm$^{-2}$) is little explored. In this article, we present charge resolved ion spectroscopic measurement of ion emission for two different cluster sizes of Ar exposed to relativistic intensities. Low charge states (${<}8$+) dominate for smaller cluster sizes and high charges states (${>}8$+) dominate the spectrum at larger cluster sizes. Electron impacting ionisation seem to be dominantly important to comprehend the charge propensity spectrum. Detailed simulations are important to decipher the role of over the barrier ionisation and electron impact ionisation.