Ion-molecule reactions and vibrational deactivation of H2+ ions in mixtures of hydrogen and helium

Ion cyclotron resonance techniques have been used to determine the thermal energy rate constants for the ion-molecule reactions: (H2+)v+H2 → lim k1H3++H,(H2+)v+ He → lim k2HeH+ + H,→ lim kv (H2+)v′ + He lim →He+ + H2 → lim k3HeH+ + H,HeH+ + H2 → lim k4H3+ + He.For a near-Franck-Condon distribution of initial vibrational states in H2+ k1 = 2.08 ± 0.03, k2 =0.13 ± 0.01, k3 0.002, and k4 = 1.83 ± 0.06×10−9 cm3/molecule· sec. Collisional deactivation of vibrationally excited H2+ ions is also shown to occur in nonreactive encounters with He atoms. The rate constant kν for this process increases with increasing vibrational quantum number ν and is approximately equal to k2v for H2+ ions in vibrational state ν.