[en] Velocity measurements of particles released from solid target surfaces exposed to a 300 eV proton plasma stream show a variety of particles with widely differing velocities. A spectroscopic doppler technique is used where two spectra of the same region, but taken from opposite directions, are imaged together on the film. This technique eliminates most of the calibration difficulties with the normal method using reference spectra, and it also gives more accurate results. Particles originating from the target bulk material are observed to be released with low energies, a few eV corresponding to less than 10³ ms^-1, as expected for physical and chemical sputtering. Some impurity particles (i.e. oxygen and carbon atoms), probably adsorbed to the surface, are however observed to be released with very high energies, sometimes several 100 eV corresponding to several times 10⁴ ms^-1 roughly equal to the plasma proton energies. (Auth.)