In this work we analyze clusters between the methoxy radical (CH3O, an open-shell molecule) and the nonpolar solvents Ar, N-2, CH4, and CF4. CH3O is formed through the photolysis of CH(3)0H vapor in a supersonic expansion of CH3OH and a solvent gas (Ar, N-2, CH4, CF4) Seeded in a carrier gas of He. The radical and solvent molecules are cooled to similar to 15-20K and form clusters. These clusters are probed using laser induced fluorescence (LIF) of the CH3O radical. An extensive set of calculations, including ab initio and atom-atom potential calculations and:rotational contour simulations are performed for each cluster in order to elucidate the cluster structure and the nature and relative importance of the limiting types of interactions that are responsible for cluster binding. A final minimum energy structure is presented for each cluster, together with the analysis of the limiting type of interactions that generate the van der Waals binding of the cluster. (C) 1997 American Institute of Physics.