Using nanoparticles to visualize the fine structure of DC glow discharge in acetylene*

DC glow discharge at low pressure in a short tube consists of a cathode layer, negative glow and Faraday dark space. A few volts deep potential well is usually present in the negative glow but this is difficult to confirm using Langmuir probes, because of the plasma disturbance. However, nanoparticles formed in the discharge and acquired a negative charge could be retained in the well. At sufficiently large concentrations and sizes, nanoparticles scatter laser radiation and can be used to visualize the shape and size of the potential well in which they are held. We have experimentally shown that the potential well in DC glow discharge in acetylene has the shape of a petal. Its dimensions depend on the gas pressure and discharge current. At low current values ​​(1 mA and below), spherical nanoparticles with a diameter of 50-100 nm are formed, which are connected into chains when the current increases.