Formation of H- ions via vibrational excited molecules produced from recombinative wall desorption of H atoms in a low-pressure H2 positive column

Recombinative wall desorption of hydrogen atoms in a low-pressure hydrogen positive column leading to formation of H-2 (X(1)Sigma (+)(g), v) molecules in optimum levels for H- production by dissociative attachment is investigated. We employed a kinetic model that solves the Boltzmann equations for electrons, coupled to a set of rate balance equations for vibrational levels H-2 (X(1)Sigma (+)(g), v), dissociated atoms H(1s) and negative ions H-. It is shown that the relative concentration [H-]/[H-2] is two times greater when recombinative wall desorption of H atoms is included in the model, for discharge pressures in the range p = 0.03-1.0 Torr and currents of 5 and 20 mA. (C) 2001 Elsevier Science BY. All rights reserved.