Low-energy electron capture by [Formula Presented] ions from atomic hydrogen using merged beams

Using the merged-beams technique, independent, absolute, total electron-capture cross sections have been measured for the [Formula Presented]+H (or D) system in the collision energy range 0.1–4500 eV/amu. For collision energies less than 200 eV/amu, the data are in reasonable accord with recent fully quantal calculations of Herrero et al. [J. Phys. B 28, 711 (1995)], except that the experiment provides no evidence for the existence of a peak in the cross section at 0.25 eV/amu. Additional structure between 10 and 100 eV/amu, as predicted by Bienstock et al. [Phys. Rev. A 33, 2078 (1986)], is not observed either. A comparison is also made with other measurements, which make use of a hydrogen furnace [Phaneuf et al., Phys. Rev. A 17, 534 (1978); Seim et al., J. Phys. B 14, 3475 (1981); Wilkie et al., J. Phys. B 18, 479 (1985)]. Above 2000 eV/amu the agreement is excellent. However, between 200 and 2000 eV/amu the present results are some 30% below the previously published experimental and theoretical cross sections, and a local maximum is found near 200 eV/amu, instead of 360 eV/amu. A possible explanation for this discrepancy is suggested.