  Our new formulation of the Spherical Collapse Model (SCM-L) takes into
account the presence of angular momentum associated with the motion of galaxy
groups infalling towards the centre of galaxy clusters. The angular momentum is
responsible for an additional term in the dynamical equation which is useful to
describe the evolution of the clusters in the non-equilibrium region which is
investigated in the present paper. Our SCM-L can be used to predict the
profiles of several strategic dynamical quantities as the radial and tangential
velocities of member galaxies, and the total cluster mass.
  A good understanding of the non-equilibrium region is important since it is
the natural scenario where to study the infall in galaxy clusters and the
accretion phenomena present in these objects. Our results corroborate previous
estimates and are in very good agreement with the analysis of recent
observations and of simulated clusters.
