J. Phys. III France
Volume 6, Numéro 9, September 1996
Page(s) 1205 - 1212
DOI: 10.1051/jp3:1996179
J. Phys. III France 6 (1996) 1205-1212

Determination of N and O Atom Density in Ar-N $_{\bf 2}$-H $_{\bf 2}$ and Ar-O $_{\bf 2}$-H $_{\bf 2}$ Flowing Microwave Post Discharges

T. Czerwiec1, J. Gavillet1, T. Belmonte1, H. Michel1 and A. Ricard2

1  Laboratoire des Sciences et Génie des Surfaces, Unité de Recherche associée au CNRS 1402, Institut National Polytechnique de Lorraine, École des Mines de Nancy, parc de Saurupt, 54042 Nancy Cedex, France
2  Laboratoire de Physique des Gaz et des Plasmas, Unité de Recherche associée au CNRS, Université de Paris-sud, Bâtiment 212, 91405 Orsay, France

(Received 8 January 1996, revised 25 April 1996, accepted 3 June 1996)

Number densities of N and O atoms have been determined using NO titration in Ar-N 2, Ar-N 2-H 2, Ar-O 2 and Ar-O 2-H 2 flowing microwave (2 450 MHz) post-discharges at 300 and 1500 Pa. The NO titration scheme is discussed from a kinetics point of view and applied to the high dilution of molecular gases in argon. The N/N 2 density ratio is enhanced by a factor 3 when small quantities of H 2 are introduced in Ar-N 2 discharges. The high O/O 2 density ratio obtained in Ar-O 2 post-discharges (0.5 to 0.6) are probably due to adsorbed H 2O that inhibits surface recombination of O-atom. The effect of H 2 addition in Ar-O 2 microwave discharge at 1500 Pa is to decrease the O atom density by homogeneous reaction involving H atoms and OH radicals.

© Les Editions de Physique 1996