We report a combined experimental and theoretical study of the electron-impact ionization of water (H2O) at the relatively low incident energy of E0=81eV in which either the 1b1 or 3a1 orbitals are ionized leading to the stable H2O cation. The experimental data were measured by using a reaction microscope, which can cover nearly the entire 4π solid angle for the secondary electron emission over a range of ejection energies. We present experimental data for the scattering angles of 6⁰ and 10⁰ for the faster of the two outgoing electrons as a function of the detection angle of the secondary electron with energies of 5 and 10 eV. The experimental triple-differential cross sections are internormalized across the measured scattering angles and ejected energies. The experimental data are compared with predictions from two molecular three-body distorted-wave approaches: one applying the orientation-averaged molecular orbital (OAMO) approximation and one using a proper average (PA) over orientation-dependent cross sections. The PA calculations are in better agreement with the experimental data than the OAMO calculations for both the angular dependence and the relative magnitude of the observed cross-section structures.



Research Center/Lab(s)

Center for High Performance Computing Research


This work was supported, in part, by the United States National Science Foundation under Grant No. PHY-1505819 (S.A., E.A., and D.M.)

Keywords and Phrases

Electron emission; Electron scattering; Electrons; Ionization; Ionization of liquids; Molecular orbitals; Molecular orientation; Secondary emission, Angular dependence; Electron impact-ionization; Orientation dependent; Reaction microscopes; Secondary electron emissions; Secondary electrons; Three-dimensional kinematics; Triple differential cross sections, Impact ionization

International Standard Serial Number (ISSN)

2469-9926; 2469-9934

Document Type

Article - Journal

Document Version

Final Version

File Type





© 2017 American Physical Society (APS), All rights reserved.

Publication Date

01 Feb 2017

Included in

Physics Commons