Measurement of the H3+ destruction rate due to ambipolar diffusion in an AC positive column discharge

We have developed a method to observe the destruction rate of H3+ in the positive column, which is limited by ambipolar diffusion. This method is based on the competition between the ambipolar diffusion rate and destruction rate by added impurities. The decrease of a velocity modulated H3+ absorption signal was studied when small amounts of CH4, N2, and CO were added to a pure hydrogen AC positive column discharge. The destruction rate constant of H3+ due to ambipolar diffusion was then obtained using a steady-state model and previously reported ion-neutral reaction rate constants.