The catalytic decomposition processes of NH3 on heated W and Ru-coated W wires were examined by employing laser spectroscopic and mass spectrometric techniques. Laser spectroscopic measurements show that more H atoms are produced on uncoated W wires, while the NH-radical densities are higher for Ru-coated wires, at the same wire temperatures. Mass spectrometric measurements show that the decomposition efficiencies are nearly the same in both systems. The main products on heated W wires must be NH2 and H, while the production of NH should also be important on Ru-coated W wires. (C) 2011 Elsevier B.V. All rights reserved.