We present theoretical fully differential cross sections (FDCS) for electron-impact excitation-ionization of helium in which the final state He+ ion is oriented in a particular direction. Specifically, we study the process for He+ ions in the 2p0 state. Using our 4-body distorted wave model, we show a strong dependence of the FDCS on the ion’s orientation and trace some unexpected structures in the FDCS to the L = 2 term in the partial wave expansion for the ionized electron. A comparison is drawn to the ionization of oriented Mg (3p0) atoms, and unlike that process, we find that for excitation-ionization angular momentum must be transferred from either the projectile or the target atom.

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We present theoretical three-dimensional fully differential cross sections for electron-impact excitation-ionization of helium when the ionized electron is found outside of the scattering plane. Using our first born approximation and 4-body distorted wave models, we examine the effect of the projectile in the initial and final states. Our calculations show that the inclusion of projectile interactions results in an increase in the magnitude of the recoil lobe.

We present experimental and theoretical results for electron-impact-induced ionization and excitation of helium atoms. Using a high-sensitivity and high-resolution (e, 2e) spectrometer, we measured the differential cross sections of ionization-excitation of He to the n = 1−5 states of He + at an impact energy of 600 eV. The experimental results are compared with 4-body distorted wave (4DW) calculations and first Born approximation (FBA) calculations. It was found that 4DW can well describe the shapes of the cross sections of the ionization with a simultaneous excitation. The cross-section ratios of excited states n = 2−5 to the ground state n = 1 were underestimated by FBA and 4DW calculations, indicating the need for further improvement of the theoretical methods.

Teresa Esposito obtained her PhD (2018) from Ghent University with a dissertation entitled Peter Paul Rubens and the Distribution of Secret Knowledge in Antwerp and Italy. Previously she worked as a research assistant at the Rubens House in Antwerp, where she contributed to several exhibitions (Room for Art in Seventeenth-Century Antwerp, 2009-2010; Palazzo Rubens. The Master as Architect, 2011). Her research is situated at the crossroads of art history, the history of science, and philosophy in the early modern period, with a particular focus on the Low Countries. She is a member of the Sarton Centre for History of Science at Ghent University and is currently a visiting scholar at the Rubenianum, Antwerp. She has published in several international peer-reviewed journals as well as in journals aimed at a larger audience of non-experts.