Recombination of neutral hydrogen atoms on AISI 304 stainless steel surface

The recombination coefficient of neutral hydrogen atoms in the ground state on polycrystalline AISI 304 stainless steel surface was determined experim entally. The H source was an inductively coupled RF hydrogen plasma with th e density of 10(16) m(-3) and the electron temperature of 6 eV. The gas fro m the discharge vessel was leaked into another vessel through a Schott 8250 glass tube with the inner diameter of 5 mm and the length of 6 cm. Charged particles created in the discharge vessel were effectively recombined on t he walls of the glass tube, so that the gas entering the experimental chamb er was solely a mixture of neutral hydrogen atoms and molecules. The densit y of hydrogen atoms in the experimental chamber was measured with a well ac tivated nickel catalytic probe. The H density depended on pressure in the d ischarge vessel and was between 3 and 19 x 10(20) m(-3.) The nickel catalyt ic probe was replaced with an identical probe made of stainless steel. Afte r successful activation of the stainless steel surface, the signal due to a tomic hydrogen recombination was measured at different pressure. Comparing the results obtained with the nickel probe and the stainless steel disc ena bled determination of the recombination coefficient for the reaction 2H --> H-2 on polycrystalline stainless steel surface: gamma = 0.10. (C) 1999 Els evier Science B.V. All rights reserved.