Plasma in supercritical fluid with densely populated clusters

Abstract

In supercritical fluid (SCF) with dense population of stable clusters (∼ 1000 mm−3; mean size ∼ 200 nm), elongated plasmas are produced along the optical axis of laser pulse (532 nm, 6 ns, 400 mJ, peak intensity ∼ 1 TW/cm2). The plasma has a strong afterglow with the lifetime up to 1 µs, increasing with the number density of clusters. For argon SCF plasmas, the electron temperature and density estimated from continuum emission spectra are ∼ 1 eV and ∼ 10^21cm−3, respectively, corresponding to a high Coulomb coupling constant of the order of unity. The radial diffusion is weak, smaller than the diffusion length predicted by the one-component plasma theory for moderate to strong Coulomb coupling. These observations suggest that the presence of clusters strongly affects the particle and energy transport processes.