Abstract Vibrational distribution of H 2 and D 2 molecules emitted from tungsten surface exposed to the continuous flow of partially dissociated neutral hydrogen gas is studied. A special vibrational spectrometer is used for this study. Vibrational distributions can be well described by vibrational temperatures being T V = 3700 ± 100 K for H 2 and T V = 3400 ± 100 K for D 2. To gain more detailed information on the state of the tungsten surface we employed ion beam analytical method ERDA for in situ determination of H/D concentration. Both experiments indicate high importance of impurity layer (presumably oxide) on the observed phenomena.