Laboratory generation of hazes in Titan's upper atmosphere using ECR plasma

Titan hazes, and their laboratory analogs, named tholins, have been extensively studied in the laboratory. Previously, cold plasmas, such as radio frequency discharge, were the dominant plasma sources to produce energetic electrons and ions to simulate photoelectrons. In this work, the electron cyclotron resonance (ECR) discharge plasma was extended to study the formation of hazes encountered in Titan's upper atmosphere. ECR plasma has many advantages such as the electrons being cyclotron accelerated with a broad-energy-spectrum that can dissociate nitrogen, and with the temperature of the ions and neutrals remaining at room temperature. In addition, ECR plasma is free of radio-frequency interference, which ensures that the background parameters and processes can be precisely measured. The N2/CH4 gas mixtures were discharged under different pressures and CH4 mixing ratios, and the basic plasma parameters, emission spectra and gas composition, as well as the parameters related to the molecular weight functional groups of the reaction products were detected simultaneously during the reaction. The optical emission spectra show that the increasing production of CN species was observed with the addition of CH4. In addition, the solid products were collected and analyzed using infrared spectroscopy and mass spectrometry, and the results are generally consistent with previous works. In summary, the ECR plasma has unique advantages and can provide an alternative energy source to study the generation of hazes encountered in Titan's upper atmosphere.