LABORATORY STUDIES ON THE FORMATION OF CN CONTAINING MOLECULES IN THE ATMOSPHERE OF TITAN AND PREBIOTIC EARTH

摘要

The reactions of excited nitrogen atoms, N(~2D), with methane, ethene and ethyne, have been studied under single collision conditions in order to identify possible reaction products. In all cases, the nitrogen/hydrogen exchange channel was found to be a significant reaction pathway, leading to nitrogen containing molecules or radicals. The present laboratory studies are helpful in modeling the chemistry of the upper atmosphere of Titan, since they confirm that reactions of N(~2D) are effective in generating new C-N bonds and therefore represent potential first steps towards the formation of nitriles. Relevant to the organic chemistry of Titan atmosphere are the following findings: ⅰ) CH_2NH is the main reaction product from the reaction N(~2D)+CH_4; ⅱ) the products of formula C_2H_3N generated by the N(~2D)+C_2H_4 reaction are formed with enough internal energy to easily rearrange to the most stable isomer CH_3CN; ⅲ) the main product from N(~2D)+C_2H_2 reaction is HCCN. We recall that both CH_2NH and CH_3CN have been observed in the atmosphere of Titan, while the HCCN radical has been suggested to be a key intermediate towards C_2N_2/C_2N_4 formation.