Rate Coefficients for H$_{3}^{+}$ Production Measured in an RF Ion Trap

The reaction H$_{2}^{+}$ + H$_{2} \rightarrow$ H$_{3}^{+}$ + H is studied using a quadrupole radio frequency ion trap coupled with a time of flight mass spectrometer. Protonated molecular hydrogen is one of the most abundant ions in the universe, and is believed to be responsible for the formation of many molecular ions in, for example, the interstellar medium and the aurorae of Jupiter. Also, since this ion is the simplest polyatomic molecule, it can be used as a basis for comparison with other polyatomic molecules. H$_{2}^{+}$ is created in a RF ion trap by electron bombardment of H$_{2}$, and then allowed to react with H$_{2}$ for varying time intervals before the H$_{2}^{+}$ and H$_{3}^{+}$ populations are ejected from the trap and detected with an active-film electron multiplier. A number of different experimental parameters (H$_{2}$ pressure, trapping parameters and electron bombardment conditions) are explored and preliminary rate coefficients for the H$_{2}^{+}$ + H$_{2} \rightarrow$ H$_{3}^{+}$ + H reaction are presented.