Mechanisms for the formetion of HCN and HNC on the intersteellar dust grains

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Experimental simulation was made for the elucidation of solid-phase reactions taking place on the interstellar dust grains. The cryocooler and a quadrupole mass spectrometer were housed in a vacuum chamber. Infrared spectra of products formed by the reaction of H atoms with deposited samples on the silicon substrate were measured using a FT-IR spectrometer. The hydrogen atoms were produced by the dc glow discharge using the bottle-neck discharge tube having two optical traps. The UV light from the H_2 plasma was completely absorbed by the graphite coated on the optical traps. When the grounded Mo wire included in the optical trap wasused, electrons effusing from the discharge tube were completely annihilated, The CN radicals formed by the discharge of N_2/CO mixed gas were deposited on the silicon substrate and reacted with H atoms. The HNC/HCN products were measured by means of FT-IR.In addition, ON radicals were also formed by the UV irradiation of (CN)_2. The reaction of C_2 hydrocarbons with H and D atoms were also investigated, It was found that acetylene was much less reactive than ethylene toward H atoms at cryogenic temperature.