Existence of four-body molecules

The existence of four-body molecules is intensively investigated using the Rayleigh-Ritz variational method within the framework of the theory of four-body systems. Special attention is devoted to the optimization of the nonlinear parameters included in the wavefunctions describing the molecular structures considered. It is shown that the theory is verified and all predicted properties of the molecules are satisfied. The optimized wavefunctions are employed for calculating the binding energies and internal distances of these molecules. The results are considered (particularly for Ps₂) as an improvement upon preceding results obtained by other authors.