Electron capture into the n = 3,4 states of H by low-energy H+, H2+ impact on gases

Absolute cross sections for electron capture into the n=3,4 states of H have been measured for 0.3-3.0-keV H⁺, H₂⁺ impact on H₂, N₂, Ar, CO₂. This cross section decreases exponentially with decreasing impact velocity according to an $\sigma =Aexp\left(\frac{-B\left|\Delta E\right|}{v}\right)$ relationship, where |Δ E| is the internal energy of the reaction, v is the ion velocity, and A and B are constant.