Ionization of molecules by electron impact represents one of the most fundamental interactions in nature, whose interest is relevant to a wide range of applications. Kinematically complete (e,2e) experiments, in which the energies and momenta of all final-state particles are determined, provide the most detailed information on the ionization reaction through the triple differential cross-section (TDCS). Compared to the case of atomic targets, performing such measurements on molecules is made difficult because of the close spacing between electronic states and also because of the contributions of rotational and vibrational states. Moreover, TDCS measurements on an absolute scale are scarce. Theoretically, finding an accurate quantal description of multicenter continuum states is a formidable task which necessarily requires some approximations.
To this end, we have proposed [1] a model, named M3CWZ, in which all continuum particles are represented by Coulomb waves with spatially variable charges; the model accounts for exchange effects and post-collision interactions.
Recently [2], we used this M3CWZ model to examine the ionization of water and methane molecules. For low impact energy on water, the results of our calculations satisfactorily reproduce absolute experimental data at 65 eV. For methane, satisfactory agreement is found but only for outer-shell ionization. As with other models presented in the literature, such as M3DW and MCTDW, experimental–theoretical agreement is not uniform, with several features left unexplained. It turns out that our M3CWZ model globally manages—at a moderate computational cost—to capture multicenter distortion effects, providing results similar in quality to those of other more sophisticated (but more computationally expensive) models.

[1] A. Tamin et al 2024 J. Chem. Phys. 161 16430.
[2] A. Tamin, Phd thesis, Sétif, Algeria (2025)