12:00 PM - 12:15 PM
[MIS12-10] In-situ IR measurement in homogeneous nucleation process of alumina under μG environment
In-situ IR measurement during nucleation of nanoparticles in the gas evaporation method proved multi-step formation of metal oxide from vapor to crystalline via liquid droplet in our ground based experiment . Using our advanced technique, we measured IR spectra of nucleating alumina and its evolution while nanoparticles are free-flying under μG environment in which Λ approximates to the value at dust formation region. Specially designed experimental apparatus equipped with dispersive IR spectrometer was loaded to S-520-30 sounding rocket by which the apparatus carried to altitude of 312 km. We also performed ground based experiment combined with FT-IR.
IR spectra of nucleating alumina measured in ground based experiment showed broad absorption extending >11 μm. Formed nanoparticles were observed by TEM and identified to δ-alumina. In contrast, sharp absorption centered at 13 μm was appeared in μG experiment. This 13 μm band is one of the most indicative features of corundum (α-alumina) sphere. Corundum is the most plausible candidate for the origin of unidentified 13 μm feature which is often observed for oxygen rich AGB stars with low-mass loss rate [5, 6]. Polymorphic behavior of alumina in homogeneous nucleation process at different Λ will be the key to understand astronomical dust formation.
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