Soft X-ray Absorption/Emission Spectroscopy and Atomic Hydrogen Irradiation Effect of Ammonia Borane

Soft X-ray absorption and emission spectra near the K-edges of B and N in ammonia borane (NH3BH3) powder are measured. These spectra show a solid crystalline spectral shape rather than a molecular spectrum. The calculation result of partial density of states by a cluster model is in good agreement with the measured spectral shape. In addition, for the purpose of investigating the reaction mechanism of ammonia borane, atomic hydrogen is irradiated, and in-situ observation is performed by soft X-ray spectroscopy. It is observed that pi* absorption splits into six peaks in the B-K absorption spectrum under atomic hydrogen irradiation. Of these, the four peaks on the high-energy side are identified as hexagonal boron nitride (h-BN) and its O-substituted chemical species.