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Project Progress

Cosmic Ice Laboratory: Organic Synthesis in Energetically Processed Ices

We completed laboratory investigations of the low temperature chemistry of acetonitrile, propionitrile, acrylonitrile, cyanoacetylene, and cyanogen (CH₃ CN, CH₃ CH₂ CN, CH₂ CHCN, HCCCN, and NCCN, respectively). Trends were sought, and found, in the photo and radiation chemical products of these molecules at 12 – 25K. In the absence of water, all of these molecules isomerized to isonitriles, and CH₃ CN, CH₃ CH₂ CN, and (CH₃)₂ CHCN also formed ketenimines. In the presence of H₂O, no isonitriles were detected but rather the isocyante ion (OCN-) was seen in all cases. Although isonitriles, ketenimines, and OCN- were the main focus of this work, we also examined cases of hydrogen loss, to make smaller nitriles, and hydrogen addition (reduction), to make larger nitriles. HCN formation was also seen in most experiments. The results are directly applicable to the nitrile ice chemistry on Titan, in cometary ice, and in the interstellar medium.

Start-up activities include:

• The Van de Graaff accelerator used for the generation of the proton beam is being rebuilt to increase beam current and to improve beam positioning and stability. The final stages of this process are nearly complete and a test beam should occur by June 20.
• A new Nicolet infrared (IR) spectrometer and a new cryostat have been installed. The spectrometer is more sensitive and has near-IR capability whereas the cryostat’s 6.5K temperature will permit H trapping in ices.
• We will include a simulation of the solar nebula x-ray environment (1-10 keV x-rays are observed for many protoplanetary nebulae). X-rays in this energy range interacting with ice predominantly generate photoelectrons with the same energy. We have visited both an x-ray and electron irradiation facility to evaluate the experimental capabilities and limitations of these beams. A decision about the purchase of similar instrumentation should be made before the end of this research year.