Abstract

The angular distribution of H⁺ fragment ions produced in 5–25 keV H⁺–H₂ collisions was investigated in coincidence with Lyman-α photons. The observed photons arise from electron capture to the projectile H(2p) state and/or from the fragmentation of the H₂ molecule via 2sσ_g, 2pσ_u or 2pΠ _u states of the excited H⁺₂^* ion. An analysis of the measured angular distributions has been performed to distinguish the separate degenerate channels available to an emitted Lyman-α photon. The results show similarities to the data of Lindsay et al. (1987) who measured the non-coincident angular distribution of H⁺ fragment ions within the same energy range.