Absence of discrete spectrum of the Schrödinger operators of positive molecular ions

For multiatomic positive molecular ions with $N$ electrons and charges $Z_i$ of the nuclei it is shown that there are no bound states for $Z_i>\gamma N$ for some $\gamma$. It is also shown that the discrete spectrum of the Schrödinger operator of a molecular ion is empty if for at least some of the nuclei the condition $Z_i\gg N$ is satisfied, whereas the charges of the other nuclei can be small.