“…In this respect, the ARs (6), (7) overestimate the total cross section for H + + NH 3 , because they are based on data for collisions with N 2 , and the electrons are released more easily from the π orbitals of N 2 than from the N-H σ bonds of NH 3 . There is a general good agreement betwen our results and the CDW-EIS calculations of references [19,21] and [23] for energies above that of the maximum of the corresponding TCS, while these calculations underestimate the cross sections at low energies, as can be observed by comparison with the experimental data and the CTMC calculation [20] for H + + H 2 O collisions. As a conclusion of these comparisons, the additivity rules (2) -(9) are useful to estimate total cross sections for electron production in proton collisions with small molecules in a wide energy range, 10 ≤ E ≤ 1000 keV.…”