Electronic energy transfer in near-resonant electron capture collisions of H+2 with metal atoms: Radiative and nonradiative transitions

Abstract

Modes of energy disposal in electron capture of H⁺₂ with metal atoms (Cs, K, Mg, and Zn) for ion velocities in the range 3–7×10⁷ cm/s are examined using combined optical and beam scattering techniques. Radiative and nonradiative transitions are observed for processes occurring under near resonant conditions. The following branching sequences are identified: Branching ratios are dependent on the vibrational state and the nuclear separation (Franck–Condon factors) of the H⁺₂ ion at the time of electron capture. The branching ratio decreases for the (triplet)/(singlet) formation for H₂ produced from reactions of vibrationally relaxed H⁺₂ ion with K or Cs. Under conditions of H⁺₂ ion relaxation, the kinetic energy of scattered atomic hydrogen following radiative decay from ³Σ⁺_g state of H₂ increases, implying a shift in the ³Σ⁺_g→³Σ⁺_u continuum toward longer wavelengths. The results also show that, at these velocities, the reations occur under near‐resonant conditions with vertical transitions.