Investigations of CH₄, C₂H₂and C₂H₄dusty RF plasmas by means of FTIR absorption spectroscopy and mass spectrometry

Abstract

Infrared (IR) absorption spectroscopy and mass spectrometry have been simultaneously applied to dusty radiofrequency (RF) plasmas in methane, acetylene and ethylene. The combination of IR absorption spectroscopy and mass spectrometry allows the chemical composition and structure of the most relevant plasma-produced neutral species, the ionic plasma composition and the chemical composition of the nanometer-sized particles to be precisely identified. The production of acetylenic compounds (C2Hx) seems to be a key mechanism for the powder formation in all the investigated hydrocarbon plasmas. Electron attachment to acetylenic compounds and the following ion-neutral reactions might lead to the high-mass carbon anions, which are trapped in the plasma and finally end in powder formation. The hydrogenation of the monomer strongly influences the composition of the ions. Finally the composition of the plasma-produced particles is mainly sp3 bonded carbon and the infrared spectra show similarities to that of polyethylene.

Diagnosis of Active Species in Reactive Acetylene Plasma by Laser-Ionization Molecular-Beam Time-of-Flight Mass Spectrometry

“…Besides these commonly observed species in some literature works [14,15,27,28], a much more abundant of C x H y (in Fig. 7) were recorded in our mass spectra with well resolved mass peaks.…”

Negative ion chemistry in Titan's upper atmosphere

“…According to the spectral pattern of the mass spectrum of the negative ions in an acetylene discharge, the repeated insertion of acetylene molecules results in an anion sequence with anions that peaks at the C 2n H -species (Deschenaux et al, 1999). Therefore, C 2 H -anions can trigger a consecutive chain of polymerization reactions that evolves as follows:…”

Dust particles in low-pressure plasmas: Formation and induced phenomena

“…In this last case, the fundamental requirement is the presence of molecular precursors [11]. These precursors result from the presence of reactive gases (silane SiH 4 [5,[12][13][14][15][16], methane CH 4 [17][18][19], acetylene C 2 H 2 [17,20,21]) or from material erosion (physical or chemical) at the molecular level [22][23][24][25][26]. They initiate a complex succession of chemical and physical reactions, leading to the growth of dust particles.…”