  During the last years some interesting experimental results have been
reported for experiments in N20, N0 , N0 dimer , H2 , Toluene and BaFCH3
cluster. The main result consists in the observation of molecular beam
depletion when the molecules of a pulsed beam interact with a static electric
or magnetic field and an oscillating field (RF). In these cases, and as a main
difference, instead of using four fields as in the original technique developed
by I.I. Rabi and others, only two fields, those which configure the resonant
unit, are used. That is, without using the nonhomogeneous magnetic fields.
  The depletion explanation for I.I. Rabi and others is based in the
interaction between the molecular electric or magnetic dipole moment and the
non-homogeneous fields. But, obviously, the change in the molecules
trajectories observed on these new experiments has to be explained without
considering the force provided by the field gradient because it happens without
using non-homogeneous fields.
  In this paper a theoretical way for the explanation of these new experimental
results is presented. One important point emerges as a result of this
development, namely, the existence of an until now unknown, spin-dependent
force, which would be responsible of the aforementioned deviation of the
molecules
