The well known existence of vibrational spectra in molecules implies simplicity of the corresponding molecular wavefunctions. This simplicity suggests the existence of quasiparticles with an approximate harmonic oscillator Hamiltonian. The conventional adiabatic approximation is known to reproduce the energy differences of the observed vibrational states. In spite of this it is shown that the adiabatic wavefunctions do not have the simplicity of approximate harmonic oscillator states. In particular, in the adiabatic wave functions the relative distances between the nuclear coordinates are selected to be dynamical variables. This article shows that with such a choice the conjugate momenta density functions could be far from the harmonic oscillator predictions. It is thus concluded that the spacing of the observed molecular vibrational states cannot be used to predict the probability distributions of relative nuclear coordinates or momenta.