The electron scatterings from isovalent molecules like O$_3$, S$_3$, OSO and SOS are studied using single centre expansion (SCE) approximation. The elastic differential cross-sections, integral and momentum transfer cross-sections are computed for these targets from ionisation threshold to 5 keV. The molecular wave functions of the targets were obtained from the multicentre expansion of the Gaussian-type orbitals within the single determinant Hartree–Fock self-consistent field scheme. The multipole expansion of the target at the centre of mass includes the dipole and quadrupole terms. The target interactions are modelled within the local potential approximation and consist of static, correlation-polarisation and exchange effects. The results are in good agreement with the available experimental and theoretical results. The SCE results match smoothly near the ionisation threshold with the {ab-initio} R-matrix results. This helped in estimating the scattering cross-section data from 0.1 to 5 keV energy. The totalcross-sections obtained by summing the elastic and inelastic cross-sections are also in excellent agreement with the available results. The scattering study from isovalent molecules further helped in understanding the effects of dipole moment, polarisation and geometrical size while evaluating the collision problem.

The partial ionisation cross-sections are reported for cations formed due to electron-impact dissociative ionisation of ethanol by invoking a variant of binary-encounter-Bethe (BEB) model. Being an important molecule in astrophysical and combustion plasma, the cross-sections are required to model this process over an extensive energy range. These are the only theoretical calculations to validate the experimental data. The approach followed is extremely simple and appears effective to estimate the cross-section data for any molecule or its cation. The electron ionisation mass spectrometry data are indispensable in the modelling of electron–molecule interactions. The work is important in several fields of pure and applied physics.