  We model quasi-two-dimensional two-electron Quantum Dots in a parabolic
confinement potential with rovibrational and purely vibrational effective
Hamiltonian operators. These are optimized by non-linear least-square fits to
the exact energy levels. We find, that the vibrational Hamiltonian describes
the energy levels well and reveals how relative contributions change on varying
the confinement strength. The rovibrational model suggests the formation of a
rigid two-electron molecule in weak confinement and we further present a
modified model, that allows a very accurate transition from weak to strong
confinement regimes.
