Energy levels of the weakly interacting radicals are estimated on the
basis of planar methyl radical interaction as a model. These levels de
pend on the given separation r between the centers of mass. The approp
riate Schrodinger equation is solved by using the Brillouin-Wigner ser
ies method. Analytical forms for the integrals used to estimate matrix
elements are derived. The principle of total momentum conservation is
strictly obeyed. Some energy levels cannot be estimated as a result o
f divergence.