To demonstrate the fundamental meaning of the introduced quantities we relate them to the criteria of Mott 8 and Hubbard 9 for onsets of localized (atomic) behavior. This is because the evolution of molecular H 2 (electron-paired) state into individual separate singly occupied (atomic) states is regarded as equivalent to the Mott-Hubbard localization (for recent related discussion in different context see e.g. ). Namely, we define Mott and Hubbard onset criteria as