Electronic energy transfer in near-resonant electron capture collisions of H2+ with metal atoms: Radiative and nonradiative transitions
- Gregory I. Gellenea(Author),
- ,
- Richard F. Portera(Author),
- Charles E. Burkhardtb(Author),
- Jacob J. Leventhalb(Author)
- aCornell University,
- bUniversity of Missouri-St. Louis
Abstract
Modes of energy disposal in electron capture of H2+ 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: Zn + H2+(Χ 2∑ g+) → Zn+ (4s, 2S) + H 2 (b 3∑u+) → 2H(1s, 2S) → Zn (4p, 1P) + H2+ (Χ 2∑g+)→hv Zn (4s 2, 1S), → H2 (Χ 1∑ g+) + Zn+ (4p, 2P) →hv Zn+ (4s, 2S), Mg + H2 + (Χ 2∑g+) → Mg + (3s, 2S) + H2 (b 3∑ u+) → 2H (1s, 2S) → H2 (Χ 1∑g+) + Mg+ (3d, 2D) →hv Mg+ (3p, 2P) →hv Mg+ (3s, 2S) → H2 (Χ 1∑g+), v″ = n) + Mg + (3p, 2P) →hv Mg+ (3s, 2S), K (Cs) + H2+ (Χ 2∑ g+) → K+ (Cs+) + H2 (a 3∑g+) →hv H2 (b 3∑u+) → 2H (1s, 2S) → K+ (Cs+) + H2 (B 1∑ u+) →hv H2 (Χ 1∑g+) → K+ (Cs+) + H2 (b 3∑u+) → 2H (1s, 2S). Branching ratios are dependent on the vibrational state and the nuclear separation (Franck-Condon factors) of the H2+ ion at the time of electron capture. The branching ratio decreases for the (triplet(/(singlet) formation for H2 produced from reactions of vibrationally relaxed H2+ ion with K or Cs. Under conditions of H2+ ion relaxation, the kinetic energy of scattered atomic hydrogen following radiative decay from 3∑ g+ state of H2 increases, implying a shift in the 3∑g+ → 3∑ u+ continuum toward longer wavelengths. The results also show that, at these velocities, the reations occur under near-resonant conditions with vertical transitions.