Mechanisms of SiO oxidation: Implications for dust formation
arXiv:2303.05184 · doi:10.3389/fspas.2023.1135156
Abstract
Reactions of SiO molecules have been postulated to initiate efficient formation of silicate dust particles in outflows around dying (AGB) stars. Both OH radicals and HO molecules can be present in these environments and their reactions with SiO and the smallest SiO cluster, SiO, affect the efficiency of eventual dust formation. Rate coefficients of gas-phase oxidation and clustering reactions of SiO, SiO and SiO have been calculated using master equation calculations based on density functional theory calculations. The calculations show that the reactions involving OH are fast. Reactions involving HO are not efficient routes to oxidation but may under the right conditions lead to hydroxylated species. The reaction of SiO with HO, which has been suggested as efficient producing SiO, is therefore not as efficient as previously thought. If HO molecules dissociate to form OH radicals, oxidation of SiO and dust formation could be accelerated. Kinetics simulations of oxygen-rich circumstellar environments using our proposed reaction scheme suggest that under typical conditions only small amounts of SiO and SiO are formed and that most of the silicon remains as molecular SiO.
arXiv comment10 pages, 13 figures
References in corpus (6)
- SiO line emission from C-type shock waves : interstellar jets and outflows
- Dust formation in the oxygen-rich AGB star IK Tau
- Too little radiation pressure on dust in the winds of oxygen-rich AGB stars
- Seed particle formation for silicate dust condensation by SiO nucleation
- Formation of silicon oxide grains at low temperature
- Bottom-up dust nucleation theory in oxygen-rich evolved stars I. Aluminium oxide clusters