COMPUTER-SIMULATIONS OF H-3(+) TRANSPORT PARAMETERS IN HYDROGEN DRIFTTUBES( AND H)

The coupled transport of H+ and H-3(+) ions in molecular hydrogen is t heoretically studied by using drift-tube-like computer simulations. Th e drift velocity and the longitudinal and the transverse diffusion coe fficients of these ions are calculated for the reduced electric field E/n (where n is the gas density) ranging from 10 to 600 Td (1 Td=10(-1 7) V cm(2)). A large influence of the rotational and vibrational H+-H- 2 excitations is noted even at low E/n for H+ ions. The presence of io n conversion reactions in collisions with background gas during the tr ansport is shown to influence the transport parameters from about 150 Td. A comparison with experimentally determined transport parameters i s performed with the aim of testing available scattering models: the c ollisional cross-section values are adjusted to get a good agreement w ith experimental ion mobilities. A relatively good agreement is obtain ed also for the longitudinal and the transverse diffusion coefficients , which indicates the consistency of the refined cross-section set. Ho wever, the transverse diffusion coefficient of H-3(+) ions exhibits la rger deviation from experimental results at higher E/n; as a possible explanation the role of proton-transfer and vibrational-excitation cha nnels in H-3(+)-H-2 collisions is discussed.