Red border for the photo-detachment from charged metallic and dielectric nanoparticles in plasmas*

The Schottky effect is predicted to decrease the energy of photons required for electron photo-detachment from metal particles negatively charged in plasma [1]. The same effect should be manifested for charged dielectric particles as well. As an example, spherical nanoparticles made from SiO₂ and Al₂O₃in the size ranging from 100 nm to 2 μm, immersed in weakly ionized nonequilibrium nitrogen plasma are considered. Our theoretical analysis has shown that the critical wavelength of the laser at which the electron photo-detachment starts (so-called the red border of the photoelectric effect) depends not only on affinity energy, but also on the charge of nanoparticles, their size and dielectric constant. The theory predicts that the smaller the size of the nanoparticles, the stronger the shift of the red border. The cross-section for the electron photo-detachment is also discussed with the Schottky effect considered. The obtained results are important for measurements of the charge and size of dust nanoparticles using a laser-stimulated photo-detachment (LSPD) technique [2]. Such measurements can provide valuable information required for modeling dusty plasmas and plasmas for the synthesis and processing of nanomaterials.  The presented theory provides guidance for the selection of the LSPD laser wavelength and analysis of the measured results.

1. M.N. Shneider, Y. Raitses and S. Yatom,  J. Phys. D: Appl. Phys. 56 29LT01 (2023)

2. T. J. A. Staps et al.,  J. Phys. D: Appl. Phys. 55, 08LT01  (2022)