Volume 625, May 2019
|Number of page(s)||8|
|Section||Atomic, molecular, and nuclear data|
|Published online||15 May 2019|
Reaction of NH+, NH2+, and NH3+ ions with H2 at low temperatures
The pathway to ammonia production in the interstellar medium
Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague, Czech Republic
Accepted: 23 March 2019
Aims. We present an experimental investigation of the exothermic reactions of NH+, NH2+, and NH3+ ions with H2 at temperatures relevant for interstellar clouds.
Methods. The reactions were studied using a variable-temperature 22-pole radio frequency ion trap instrument.
Results. The temperature dependences of rate coefficients of these reactions have been obtained at temperatures from 15 up to 300 K. The reaction of NH+ with H2 has two channels, which lead to NH2+ ( ∼ 97%) and H+3 ( ∼ 3%) with nearly constant reaction rate coefficients (kaNH+(17 K) = 1.0 × 10−9 cm3 s−1 and kbNH+(17 K) = 4.0 × 10−11 cm3 s−1, respectively). The reaction of NH2+ with H2 produces only NH3+ ions. The measured rate coefficient monotonically decreases with increasing temperature from kNH2+(17 K) = 6 × 10−10 cm3 s−1 to kNH2+(300 K) = 2 × 10−10 cm3 s−1. The measured rate coefficient of the reaction of NH3+ with H2, producing NH+4, increases with decreasing temperature from 80 K down to 15 K, confirming that the reaction proceeds by tunnelling through a potential barrier.
Key words: astrochemistry / molecular data / molecular processes / methods: laboratory: molecular / ISM: molecules
© ESO 2019
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