Nanoplasma dynamics in Xe clusters driven by ultraintense laser fields

Abstract

We present a theoretical and computational study of the properties and the response of the nanoplasma and of outer ionization in Xen clusters (n = 55–2171, initial cluster radius R0 = 8.7–31.0 A) driven by ultraintense near-infrared laser fields (peak intensity IM = 1015–1020 Wcm-2, temporal pulse length τ= 10–100 fs, and frequency ν= 0.35 fs-1). The positively charged high-energy nanoplasma produced by inner ionization nearly follows the oscillations of the fs laser pulse and can either be persistent (at lower intensities of IM = 1015–1016 Wcm-2 and/or for larger cluster sizes, where the electron energy distribution is nearly thermal) or transient (at higher intensities of IM = 1018–1020 Wcm-2 and/or for smaller cluster sizes). The nanoplasma is depleted by outer ionization that was semiquantitatively described by the cluster barrier suppression electrostatic model, which accounts for the cluster size, laser intensity and pulse length dependence of the outer ionization yield. The electrostatic model was further utilized for estimates of the laser intensity and pulse width dependence of the border radius R0 (I) for the attainment of complete outer ionization at $R_{0} \lesssim R_0^{(I)}$ , while at R0 > R0 (I) a persistent nanoplasma prevails. R0 (I) establishes an interrelationship between electron dynamics and nuclear Coulomb explosion dynamics in ultraintense laser-cluster interactions.