The hamiltonian becomes then ˆH=−ℏ2∇212m−ℏ2∇222m−2ke2r1−2ke2r2+ke2r12, and Schroedingers equation reads ˆHψ=Eψ. All observables are evaluated with respect to the probability distribution P(R)=|ψT(R)|2∫|ψT(R)|2dR. generated by the trial wave function. The trial wave function must approximate an exact eigenstate in order that accurate results are to be obtained.