Mass dependence from statistical analysis of stretching vibrational levels. Application to the linear triatomic molecule CS2

Vibrational spectra of polyatomic molecules depend on the atomic masses. Using the CS2 molecule as an example, a statistical analysis is performed for the stretching vibrational energy levels as a function of the isotopic masses. It is found that both the nearest-neighbour level spacing distribution and Δ3 statistics are modified by isotopic substitution which should have experimental consequences.