The vacuum-UV laser induced fluorescence spectrum of molecular neutral species present in an H-2/D-2 plasma expansion has been recorded from 60 500 cm(-1) to 83 500 cm(-1). It will be shown that this VUV spectrum results from X-1 Sigma(+)(g) <-> B-1 Sigma(+)(u) (Lyman) transitions in H-2, HD and D-2 molecules that are high rovibrationally excited. This is inferred from the comparison of simulated Lyman spectra based on spectroscopic data for H-2, HD and D-2 with the measured VUV spectra. (C) 2007 Elsevier B.V. All rights reserved.