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Infrared properties of nitrogen-included carbonaceous compounds
Tuesday, May 15, 2018 - 3:00pm PDT
University of Tokyo
The unidentified infrared bands (UIR) bands have been observed ubiquitously in various astrophysical environments. Polycyclic aromatic hydrocarbon (PAH) hypothesis is commonly used to interpret the behavior of the observed UIR bands, however, our knowledge on the true carriers of the UIR bands is still limited. We have synthesized Nitrogen-included Carbonaceous Compounds (NCC) by exposing hydrocarbons (e.g., Quenched Carbonaceous Composite; QCC and/or PAHs) to nitrogen plasma via 2.45 GHz microwave discharge. Infrared absorption spectra of NCC exhibit a broad feature around 8µm in addition to the features at 3.29µm, 6.25µm and 11.96µm, which are remarkably similar to the “Class C” UIR bands observed at classical novae (e.g., V2361 Cyg). The XANES analysis of NCC indicates that amine structures are included in the NCC. We conclude that amine structures contribute to the 8µm feature of NCC. The N/C ratio of the NCC is found to be 4-5% based on the EA/IRMS measurement. Our plasma chemical vapor deposition (CVD) method to synthesize NCC well simulates the process of dust formation/evolution in nova outburst ejecta. The remarkable similarity between the infrared properties of NCC and the UIR bands observed in classical novae suggests that the NCC is a strong candidate of the carrier of the UIR bands formed around dusty classical novae.