Interaction of N and O atoms with hardwood and softwood surfaces in the flowing afterglow of N 2 ‐O 2 microwave plasmas

The interaction between hardwood (Sugar Maple) and softwood (Black Spruce) surfaces and N and O atom species produced in the flowing late afterglow of a surface‐wave microwave plasma column in N 2 ‐O 2 gas mixtures was investigated using a NO titration method combined with optical emission spectroscopy. Results showed two distinct atom loss regimes following their interaction with wood surfaces: a recombination regime at low oxygen concentrations (<1% O 2 ) and an etching regime by O atoms at higher oxygen concentrations (>1% O 2 ). The etching reaction was confirmed by surface profilometry measurements, with the formation of sub‐millimetre trenches between low‐density early wood and high‐density late wood regions. Recombination dynamics of O and N atoms over smooth and roughened wood regions are also compared.