Pre-scission H1 and He4 in O16+197Au reactions are measured in coincidence with fission fragments in the compound nucleus excitation energy of 48 to 99 MeV. Observed coincident energy spectra of H1 and He4 are shifted towards lower energies compared to statistical model calculations. The data are analyzed in terms of the spin-dependent level density and emission barriers for the charged particles. The analysis shows that the effect of the spin-dependent level density on the energy spectrum is small and the effective emission barriers for particle emissions are reduced by 1.0 0.4 MeV for H1 and 1.8 0.4 MeV for He4 relative to the corresponding fusion barriers calculated by using optical potentials. © 1990 The American Physical Society.