Temperature dependence of the rate coefficient of the reaction (4). The upward pointing triangles indicate the binned values measured in the present experiments with the injection of NH ions into the ion trap. The raw data without binning are indicated with the smaller points. The stars indicate the reaction rate coefficients obtained from the [H₂] dependences (see Fig. 7). The horizontal straight line (k_L) indicates the value of the Langevin collisional rate coefficient. The values of measured in previous experiments at 300 K by Kim et al. (1975; ICR) and by Adams et al. (1980; SIFT) are indicated with the open triangles. The labels A and B indicate values of obtained in the present experiments with the injection of N⁺ ions into the trap at 16 and 18 K, respectively. The label G indicates the value of measured in similar conditions in ion trap at 15 K by Gerlich (1993).