The question of how far the concept of reflection of electrons at the
oscillating sheath can be applied to the collisional situation is inve
stigated. A radiofrequency discharge between two parallel plates is co
nsidered. Model calculations on the basis of the transport equations r
esult in two contributions to the collisional sheath oscillation heati
ng. The first contribution represents heating in an expanding sheath a
nd cooling in a contracting sheath due to reflection at the sheath edg
e. The second contribution describes Joule heating within the sheath r
ange and is of the same order of magnitude as the corresponding bulk h
eating. In the experiment a 300 kHz discharge is operated by a non-sin
usoidal voltage with a steep rise and fall to a plateau. Optical emiss
ion spectroscopy resolved in time and space is applied. Owing to the s
pecial voltage shape, emission caused by radiofrequency heating can be
separated from emission caused by secondary electrons from the cathod
e. The experimental results confirm the predictions of the model.