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The experimental determination of the reaction rate coefficients for production and destruction of HCN+ and HNC+ in collision with H2 is presented. A variable-temperature, 22-pole radio frequency ion trap was used to study the reactions in the temperature range 17–250 K. The obtained rate coefficients for the reaction of CN+ and HCN+ with H2 are close to the collisional (Langevin) value, whereas that for the reaction of HNC+ with H2 is quickly decreasing with increasing temperature. The product branching ratios for the reaction of CN+ with H2 are also reported and show a notable decrease of the HNC+ product with respect to the HCN+ product with increasing temperature. These measurements have consequences for current astrochemical models of cyanide chemistry, in particular, for the HCNH+ cation. [ABSTRACT FROM AUTHOR]

The rate coefficients k1 and k2 of the reaction $ \hbox{OD}^- + \hbox{HD} \mathop{\rightleftarrows}\limits_{k_2}^{k_1} \hbox{OH}^- + \hbox{D}_2 $ OD − + HD ⇄ k 2 k 1 ⁡ OH − + D 2 in the forward and reverse direction were measured in the temperature ranges of 15 K–273 K and 95 K–300 K, respectively. The experiments were carried out in a temperature-variable cryogenic linear 22-pole radio-frequency ion trap instrument. The temperature dependence of the equilibrium constant $ { {K_{{\rm eq}12}}}(T) $ K e q 12 (T) obtained from the measured data is in good agreement with the value calculated using the detailed balance principle under the Born-Oppenheimer approximation. The enthalpy and the entropy of the reaction obtained from the linear Van't Hoff equation are $ { {\Delta H}} = (20 \pm 2 \pm 3^{{\rm sys}})\,{\rm meV} $ Δ H = (20 ± 2 ± 3 s y s ) m e V and $ { {\Delta S}} = (5.9 \pm 1.8 \pm 1.4^{{\rm sys}})\,{\rm J}/{\rm mol}\,{\rm K} $ Δ S = (5.9 ± 1.8 ± 1.4 s y s ) J / m o l K , respectively. [ABSTRACT FROM AUTHOR]

The rate coefficients for the ternary association reaction of vibrationally cold N 2 + ions with N 2 and He were measured in an afterglow plasma in the temperature range of 140-250 K: k N 4 + = (1.02 ± 0.39)(300/ T ) (1.28±0.08) × 10 -29 cm 6 s -1 . The rotational and vibrational state populations of N 2 + ions were probed in situ by time-resolved cavity ring-down spectroscopy. The rate coefficient for Penning ionization of N 2 by helium metastable atoms was also determined: k m = [(2.70 ± 0.17) + (84.3 ± 5.9)e -(877±36)/ T ] × 10 -11 cm 3 s -1 .