Charging and propulsion of nano silicon in external electric and magnetic fields: Impact on the interstellar dust transport

Abstract

Observation of nanosilicon-based contributions to the interstellar nanodust is problematic because the indirect-bandgap of silicon makes its optical features wide, while carbon’s higher abundancy and ionization potential and the rising slope of extinction curves introduce heavy convolution. Recent macroscopic synthesis and charging of nanosilicon, the coming online of the Webb space telescope with unprecedented spectral resolution, and advances in modeling algorithms, light scattering, and fundamental atomistic computation may open opportunities for effective comparison between laboratory and space observation. Here, we study the transport of charged nanosilicon in electric/magnetic fields. We use high voltage across liquid colloids to charge and propel nanosilicon into external fields and imprint them on metal-coated substrates. We use absorption, luminescence, and light scattering in liquid, flight, and imprinted surfaces to study the field deflection of nanosilicon. We use the Mie/finite-difference time-domain theory to obtain scattering curves of nanosilicon and silica. Nanosilicon-based UV features near the 217.5-nm carbon bump are recorded and calculated using Time-Dependent Density Functional Theory (TDDFT) atomistic theory at 225, 280, and 153 nm resulting from bound–bound, and valence-continuum transitions, respectively. We also show that the constituents of silicates, oxygen and Mg and Fe metal ions, can attach to Si nanoparticles without interrupting luminescence, infrared, or UV signatures, respectively. Because charge defects allow nanosilicon transport over large distances via open B fields of solar holes as well as provide them with narrow “atomic-like” transitions, which are otherwise extended, sightlines with lower carbon and higher resolution afforded by Webb may allow the unmasking of Si-based features.