| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2006: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2005: ¥3,100,000 (Direct Cost: ¥3,100,000)
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| Research Abstract |
In this project, neutral-neutral chemical reactions, which are known to play an important role in interstellar clouds, have been studied from a theoretical viewpoint of reaction dynamics. Our goal is to provide important physical quantities including reaction rate constants and product branching rations for such interstellar chemical reactions. This is simply because it is generally accepted that experimental measurements of such quantities are very difficult tasks under very low temperature and very low density conditions.
First, we carried out quantum reactive scattering calculations for the reaction of the carbon atom with acetylene, which is known to play a role in carbon-chain growth in interstellar space. We have developed two types of reduced-dimensionality quantum scattering models and calculated rate constants as well as product branching ratios.
Next, we focused on theoretical study of the production mechanism of HNC, which has been frequently detected in interstellar medium. We studied the importance of the HNC production from the radical-radical reaction, C_2+NH, since both radicals are found in interstellar environment. We carried out electronic structure calculations of the interaction potential energy surface at accurate levels of theory. As a result, we found that the C_2+NH reaction proceeds without a barrier. We have then carried out on-the-fly direct dynamics calculations in order to identify the reaction products. After several tests, we have chosen to use the hybrid B3LYP density-functional method to save computational time. From results of these direct dynamics calculations, we found that HNC is efficiently produced via the C_2+NH reaction for the first time. Detailed analysis revealed that this is a result of dynamics, where the lifetime of the CCNH intermediate is very short. Also, it was found that momentum transfer occurs quite efficiently in the C_2+NH → C+HNC reaction.
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