CDW-EIS description of the electron impact ionization of H2O at low impact energies

ACEBAL, E.; S. OTRANTO

Budapest

Conferencia; International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces; 2018

P { margin-bottom: 0.08in; direction: ltr; color: rgb(0, 0, 0); }P.western { font-family: "Times New Roman",serif; font-size: 12pt; }P.cjk { font-family: "SimSun","宋体"; font-size: 12pt; }P.ctl { font-family: "Times New Roman",serif; font-size: 12pt; }A:visited { color: rgb(128, 0, 128); }A.western:visited { }A.cjk:visited { }A.ctl:visited { }A:link { color: rgb(0, 0, 255); }In the present work,fully differential cross sections for electron impact ionization ofgaseous H2O at an impact energy of 81 eV are calculatedwithin the framework of the continuum distorted wave-eikonal initialstate (CDW-EIS) model. Theunderstanding of the dynamics of collision processes involving H2Omolecules are of singular importance, provided that it can be used asa prototype for a biological medium and is also a common component inastrophysical environments.Inthat sense, we analyze the experimental data obtained recently by Renand co-workers [1] by means of a reaction microscope, whichcorrespond to detection of electrons emitted from either the 1b1or the 3a1 valence orbitals of H2O.Their experimental cross sections represent the sum of the separatecontributions from both orbitals. In that work, the experimental datawere contrasted to theoretical results obtained by means of thedistorted wave Born approximation (DWBA).Incontrast to the DWBA, which can be seen as a first order theory, theCDW-EIS model explicitly considers higher order terms in the initialstate correlation.Inorder to obtain fully differential cross sections, the calculation ofthe transition amplitude at fixed molecular orientations has beendeveloped by direct 6D numerical integration over the coordinatesusing an adaptive Monte Carlo scheme. Then, a proper averageprocedure was performed to mimic the experimental conditions. Weestimate our numerical uncertainty to be less than 5%.InFigure 1, we compare present CDW-EIS results for one of the fourgeometries reported for the scattering plane. Since the experimentaldata have been arbitrarily normalized to DWBA theory in ref. [1], acommon factor 0.8 is used to normalize the results of ref. [1] to ourtheoretical results. Itcan be seen, in Figure 1, that the CDW-EIS model provides a very gooddescription of the experiment for the geometry considered. While theDWBA predicts a two-peak structure in the binary region, the CDW-EIStheory predicts a single peak binary structure and a recoil to binarypeak ratio that is in better agreement with the experiment. The samesituation stands for the four geometries reported.Figure 1. CDW-EIS triply differential crosssection for electron impact ionization of 1b1 and3a1 orbitals of H2O. Kinematicconditions are indicated in the insets, for the scattering plane.Experimental and DWBA data from ref. [1] scaled to the presenttheoretical results. Inaddition, we present calculations of fully differential crosssections for electron impact ionization of the valence orbitals 1b1and 3a1 of H2O, for the denominatedsemi-perpendicular plane and full perpendicular plane. Those resultsare benchmarked against the experimental data and the DWBAtheoretical results reported in ref. [1], finding good overallagreement between the CDW-EIS theory and the experimental data. References[1]X. Ren, S. Amani, K. Hossen, E. Ali, C. G.Ning, J. Colgan, D. Madison, and A. Dorn, Phys.Rev. A (2017) 95,022701. P { margin-bottom: 0.08in; direction: ltr; color: rgb(0, 0, 0); }P.western { font-family: "Times New Roman",serif; font-size: 12pt; }P.cjk { font-family: "SimSun","宋体"; font-size: 12pt; }P.ctl { font-family: "Times New Roman",serif; font-size: 12pt; }A:visited { color: rgb(128, 0, 128); }A.western:visited { }A.cjk:visited { }A.ctl:visited { }A:link { color: rgb(0, 0, 255); }