Reaction of NH⁺, NH₂⁺, and NH₃⁺ ions with H₂ at low temperatures

Abstract

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.

Gas-Phase Reactivity of OH Radicals With Ammonia (NH3) and Methylamine (CH3NH2) at Around 22 K

“…Under the ISM conditions, it has been assumed since a long time (Herbst and Klemperer, 1973) that dissociative recombination of NH 4 + is the main provider of NH 3 in the gas phase. This cation can be generated through a series of hydrogen abstraction reactions starting from N + + H 2 leading step by step to NH + , NH 2 + , NH 3 + , and eventually NH 4 + (Gerin et al, 2016;Rednyk et al, 2019). Alternatively, NH 2 + can be produced by H 3 + + N (Scott et al, 1997).…”

Vibrationally and Spin-Orbit-Resolved Inner-Shell X-ray Absorption Spectroscopy of the NH+ Molecular Ion: Measurements and ab Initio Calculations

“…As reported in previous studies (see, for example, Reference [5] and references therein), the electronic ground state of the NH + molecular ion is a 2 In order to determine the vibrational progression and Frank-Condon factors (FC) associated with the most relevant electronic transitions emerging from the x-ray absorption (XAS) N1s inner-shell spectrum of NH + , the PEC of selected low-lying N1 s −1 core-excited states of interest have been calculated for internuclear distances ranging between 0.6 and 5 Å and are displayed in Figure 2 for the internuclear distance region between 0.6 and 3 Å.…”

“…Small molecules and their cations, notably hydrides, play important roles in laboratory and astrophysical plasma processes [1] and in planetary atmospheric chemistry. Reliable data on their electronic and vibrational structures as well as their interaction with ionizing radiation are key for their identification in astrophysical environments and an understanding of their chemical reactivity [2]. Standard gas-phase chemistry models show that NH and NH + are present at various stages of the pathways to ammonia production in the interstellar medium [1][2][3].…”

“…Reliable data on their electronic and vibrational structures as well as their interaction with ionizing radiation are key for their identification in astrophysical environments and an understanding of their chemical reactivity [2]. Standard gas-phase chemistry models show that NH and NH + are present at various stages of the pathways to ammonia production in the interstellar medium [1][2][3]. NH has been observed in diffuse clouds [4], but laboratory observations only are known for NH + .…”

Study of electron scattering from $${{\mathrm {CH}}}_{{4}}^{+}$$, $${{\mathrm {NH}}}_{{3}}^{+}$$, $${\mathrm {H}}_{{2}}{\mathrm {O}}^{+}$$, $${{\mathrm {NH}}}_{{4}}^{+}$$ and $${\mathrm {H}}_{{3}}{\mathrm {O}}^{+}$$ molecular ions with an analytic static potential approach

“…NH 3 and its protonated derivative NH + 4 are efficient NH sources via ion conversion and recombination [22]. On the other hand, nitrogen is one of the most abundant element in the universe and its nitrogen hydrides are present in the interstellar medium and in the reaction of nitrogen ions with the H 2 , it produces positive ammonium ions, i.e., NH + , NH + 2 , NH + 3 , NH + 4 [23]. It is noticed that in the coma of 67P/C-G near perihelion [24], NH + 4 ion is detected as one of the most abundant ions.…”