Measured dependences of the reaction rates and , corresponding to the production of NH and H ions, on H₂ number density. The plotted values of (corresponding to H production) are increased by a factor of 10. The mean helium number density was of the order of 10¹⁴ cm⁻³. The collisional temperature is T = 20 K. In these experiments, the primary NH⁺ ions were produced in the SIS and injected into the ion trap. The values of the binary reaction rate coefficients and obtained from the slopes of the corresponding dependences are shown in the legend.