Reaction rate constant for Ar(3P2) metastable atoms with the tetramethylsilane molecule

The reaction rate constant of Ar(3P2) metastable atoms with (Si(CH3)4 (tetramethylsilane or TMS molecule) has been studied in a microwave discharge afterglow by means of absorption spectroscopy measurements on Ar(3P2) at the 811.5 nm transition line and mass spectrometry. Among the various molecules or radicals produced by the chemical reactive process Si(CH3)x radicals are the main species. They arise from Si–C bond breaking. H2+ is also detected. This proves that the SiCxHy species (with y<3x) is also created by C–H bonds breaking. However, they are only weakly detected probably because of their low concentration. We have determined for the relative reaction branching ratio producing Si(CH3)x species: 5% Si(CH3)3, 15% Si(CH3)2 and 80% Si(CH3). Moreover we have measured a total de-excitation rate constant for the Ar(3P2) metastable atoms reacting with tetramethylsilane, ranging from 6×10−18 to 2.2×10−17 m3 s−1. This result is compared to theoretical predictions.