The important process by which the translational energy of GaCl molecules diminishes before their adsorption on the GaAs surface, in halide and hydride epitaxial growth, is difficult to study experimentally. In the present work, we study the dynamical behavior of GaCl molecules on the GaAs(0 0 1) 2 x 4 beta2 surface in order to reveal the relaxation mechanism of GaCl. At incident angles of 60degrees and 75degrees, the observed dynamical processes are in contrast to the ones predicted by the famous hard- and soft-cube models. It is shown that the high degree of surface corrugation strongly influences the dynamical behavior in general, and the relaxation processes in particular. (C) 2003 Elsevier Science B.V. All rights reserved.