Measurements of rate coefficients of CN${}^{+}$, HCN${}^{+}$ and HNC${}^{+}$ collisions with H${}_2$ at cryogenic temperatures

The experimental determination of the reaction rate coefficients for production and destruction of ${\text{HCN}}^{+}$ and ${\text{HNC}}^{+}$ in collisions with ${\text{H}}_2$ is presented. A variable temperature 22 pole radio frequency ion trap was used to study the reactions in the temperature range of $17-250\text{K}$. The obtained rate coefficients for the reaction of ${\text{CN}}^{+}$ and of ${\text{HCN}}^{+}$ with ${\text{H}}_2$ are close to the collisional (Langevin) value, whereas that for the reaction of ${\text{HNC}}^{+}$ with ${\text{H}}_2$ is quickly decreasing with increasing temperature. The product branching ratios for the reaction of ${\text{CN}}^{+}$ with ${\text{H}}_2$ are also reported and show a notable decrease of ${\text{HNC}}^{+}$ product with respect to ${\text{HCN}}^{+}$ product with increasing temperature. These measurements have consequences for current astrochemical models of cyanide chemistry, in particular for the ${\text{HCNH}}^{+}$ cation.