Molecular Orientation and Photochemical Reaction of Organoaluminum Compounds Investigated by Buried Metal Layer Infrared Reflection Absorption Spectroscopy

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Abstract
The structure and synchrotron radiation (SR) irradiation effects of the low-temperature condensed layer of several organoaluminum compounds on the SiO2 surface were investigated by infrared reflection absorption spectroscopy using a buried metal layer substrate (BML-IRAS). Trimethylaluminum is a dimer at temperatures lower than 180 K, and a photoproduct having the methyl group is produced by SR irradiation. The condensed layer of dimethylethylamine alane (DMEAA) as-deposited at temperatures less than 140 K consists of randomly oriented dimer molecules, and changes to a more ordered orientation of monomer molecules at temperatures higher than 140 K. Concerning the SR irradiations, the results are different for the two different molecular orientations. Upon SR irradiations of the ordered orientation layer, a new broad vibration band, possibly assigned to the aggregation of inhomogeneous AlH stretching vibrations, appears. On the other hand, in the case of the random orientations of the dimer molecules, such a new broad band does not appear, and only an intensity decrease is observed for all bands.