Fully Differential Study of the Ionization of H2O by Light Particle-Impact

ACEBAL, E.; OTRANTO, S

Buenos Aires

Encuentro; Encuentro Nacional de Dinámica Cuántica de la Materia; 2019

Instituto de Astronomía y Física del Espacio

The ionization of atoms and molecules by charged particles impact has been subject of many studies during the past decades. Understanding the dynamics of these processes is essential in areas such as plasma physics, astrophysics and radiobiology. In this context, the ionization of the water molecule (H2O) has acquired great interest because of its vast presence in nature, and in particular, since it can be used as a prototype for a biological medium.A complete kinematically study of these processes can be achieved through the analysis of the fully differential cross sections (FDCS). In this sense, measurements of single ionization from the two most outer valence orbitals of H2O by electron-impact at 81 eV have recently been reported. These results were accompanied by DWBA calculations and the authors concluded that higher-order terms in their theory might be relevant at this impact energy based on the discrepancies observed with the experimental data. Following this line, in a previous work, we used the CDW-EIS model to analyse those data, since it explicitly contains higher-order terms in the initial-state correlation. We improved indeed the agreement with measurements, compared to the DWBA.In this work, we focus ourselves on the influence of the projectile charge sign in the single ionization of the two most outer valence orbitals of H2O. We computed FDCS by means of the CDW-EIS model. This involved the calculation of the transition amplitude by a 6D integration, which was accomplished by an adaptive Monte Carlo scheme. A proper average procedure over molecular orientations was performed to mimic experimental conditions.We contrast positron- and electron-impact FDCS for one of the four kinematic conditions reported for the scattering plane. We observe a decrease of the recoil lobe and an increase of the binary region accompanied by a shift towards lower emission angles for positron-impact. There is also a third peak among the direction of k1, which obeys to the post-collisional interaction (PCI), just as the previous features mentioned. The same situation stands for the four kinematic conditions reported. FDCS for the denominated semi-perpendicular and full perpendicular planes are also analysed.In addition, forward electron emission is investigated identifying the electron capture to the continuum structure for positron-impact. We respectively observe a high narrow peak and a huge dip for positron- and electron-impact due to the PCI. These structures were already seen in previous ionization studies.