Iron-oxide nanoparticles have been synthesized by high temperature arc plasma route with different plasma currents and characterized for their structure, morphology and local atomic order. Fe K-edge x-ray absorption spectra reveal distinct local stru
cture of the samples grown with different plasma currents. We have shown that the local disorder is higher for the higher plasma current grown samples that also have a larger average particle-size. The results provide useful information to control structural and morphological properties of nanoparticles grown by high temperature plasma synthesis process.
We have used the free expansion of ultracold neutral plasmas as a time-resolved probe of electron temperature. A combination of experimental measurements of the ion expansion velocity and numerical simulations characterize the crossover from an elast
ic-collision regime at low initial Gamma_e, which is dominated by adiabatic cooling of the electrons, to the regime of high Gamma_e in which inelastic processes drastically heat the electrons. We identify the time scales and relative contributions of various processes, and experimentally show the importance of radiative decay and disorder-induced electron heating for the first time in ultracold neutral plasmas.
