Interference effects for intermediate energy electron-impact ionization of H 2 and N 2 molecules (original) (raw)
Related papers
Two-center interference in electron-impact ionization of molecular hydrogen
Physical Review A, 2018
Fast (E 0 = 520 eV) electron-impact ionization of molecular hydrogen (H 2) is studied experimentally and theoretically for a resolved molecular axis angle and 10 eV ejected electron energy. Fully differential cross sections were measured using an electron-electron-ion triple coincidence experiment in which the molecular axis direction is obtained for ionic ground-state dissociation. While predictions from the standard two-wave interference model are in strong disagreement with experiment a multicenter distorted-wave method obtains much better results. This demonstrates the importance of the multicenter ionic potential for the electron emission pattern at low energy and the failure of hitherto widely used simple models which treat molecular ionization as the coherent sum of atomic ionization amplitudes.
Triple Differential Cross Section For Electron Impact Ionization of H 2 and N 2 Molecules
2013
The interest in ionization of diatomic molecules, such as N2 and H2, by charged particle impact sparked the quest for interference effects similar to Young’s two-slit experiment. Young type interference effects resulting from the coherent superposition of the scattered waves from two atomic centers were recently predicted by Stia [1] et al. and by Gao et al. [2] for electron impact ionization of molecular hydrogen and molecular nitrogen, respectively. Measurements on the investigation of interference effects on TDCS spectra was reported by several groups [3,4]. The question than is how interference effect changes due to scattering angle or to ejected electron energy in TDCS spectra. The (e,2e) technique investigates electron impact ionization, and provides the most detailed insight into the reaction of many-body systems. However, due to the small cross sections, the experimental investigations of the ionization of small molecules by this technique are very limited. In this context, ...
Journal of Electron Spectroscopy and Related Phenomena, 2007
Experimental and theoretical work studying the (e,2e) collision process from diatomic molecules is reported. In particular, recent work carried out from near threshold to ∼100 eV incident electron energy ionizing H 2 and N 2 in coplanar symmetric and asymmetric geometries is compared to calculations using a molecular three body distorted wave model. Of interest is the possibility of observing the effects of Young's double slittype interference terms in the measured cross-sections. There is considerable interest in this type of scattering, since simple models predict the effects should be equivalent to a modulation of the cross-section from individual atoms which constitute the molecule. Such effects have recently been inferred at 250 eV incident energy in an asymmetric geometry, however at lower energies the complexity of the scattering process and the requirement to integrate over all possible alignments of the targets means that these effects remain unclear. Experimental data and results from a molecular three-body distorted wave (M3DW) model are presented, and possible methods to experimentally align and detect the molecular direction prior to ionization are suggested.
Observation of two-center interference effects for electron impact ionization of N 2
Journal of Physics B: Atomic, Molecular and Optical Physics, 2015
In 1966, Cohen and Fano (1966 Phys. Rev. 150 30) suggested that one should be able to observe the equivalent of Young's double slit interference if the double slits were replaced by a diatomic molecule. This suggestion inspired many experimental and theoretical studies searching for double slit interference effects both for photon and particle ionization of diatomic molecules. These effects turned out to be so small for particle ionization that this work proceeded slowly and evidence for interference effects were only found by looking at cross section ratios. Most of the early particle work concentrated on double differential cross sections for heavy particle scattering and the first evidence for two-center interference for electron-impact triple differential cross section (TDCS) did not appear until 2006 for ionization of H 2. Subsequent work has now firmly established that two-center interference effects can be seen in the TDCS for electronimpact ionization of H 2. However, in spite of several experimental and theoretical studies, similar effects have not been found for electron-impact ionization of N 2. Here we report the first evidence for two-center interference for electron-impact ionization of N 2 .
Search for interference effects in electron impact ionization of aligned hydrogen molecules
Journal of Physics B: Atomic, Molecular and Optical Physics, 2010
Five-fold differential cross sections (5DCS) for electron impact ionization of a diatomic molecule have been explored experimentally as a function of molecular alignment. Using H 2 as a test system we exploited dissociative ionization by 200 eV electrons to obtain the alignment of the internuclear axis. Separation of groundstate ionization from autoionization is discussed. 5DCS are investigated for the direct channel and found to be in good agreement with M3DW calculations discarding at the same time a simple two-centre interference model discussed recently in literature.
Interference effects in single ionization of molecular hydrogen by electron impact
Journal of Physics B: Atomic, Molecular and Optical Physics, 2003
A recently developed molecular three-continuum approximation is employed to compute differential cross sections for the ionization of hydrogen molecules by electron impact. Within the framework of this approximation, the chosen final electronic wavefunction takes into account the molecular character of the target as well as the correlate motion between the aggregates in the final channel of the reaction. Fivefold-differential cross sections as a function of both the electron momenta in the final state and the molecular orientation are studied for different kinematical arrangements. Interference structures coming from the two-centre geometry of the molecule are predicted in this case. Integrated cross sections over all molecular orientations are also calculated. It is shown that interference patterns remain, even for this case.
Theoretical study of electron impact-ionization of molecules
There has been impressive progress in the area of theoretical treatments of electron impact ionization (e,2e) of atoms and molecules in the last decade. Most recently, low to intermediate incident electron energies have been reported for molecular systems. In this dissertation, different theoretical models will be used to calculate the fully differential cross section (FDCS) for (e,2e) processes for low to intermediate incident electron energies for a variety of final state electron angles and energies for the diatomic molecules H2 and N2, the triatomic molecule H2O, and the boimolecule HCOOH. In addition, there has been a large amount of interest in diatomic molecules inspired by the possibility of observing an interference effect due to the two molecular centers playing the role of a double slit. In this dissertation, the interference effect for the diatomic molecules H2 and N2 will be examined. Finally, there is presently considerable experimental effort directed towards measurin...
Recent theoretical progress in treating electron impact ionization of molecules
Journal of Physics: Conference Series, 2010
e,2e) ionization differential cross sections are presented for several molecules. We will compare experimental results with theoretical calculations using the molecular three body distorted wave (M3DW) approximations for H 2 , N 2 , H 2 O and Formic Acid (FA) using better wave-function for the molecules than we had in previous works. Generally, good agreement is found between the M3DW approach and experiments.
Electron Impact Ionization Cross Sections of H2 for Low Excess Energies Ranging from 2eV to 20eV
2009
We had recently investigated the nuclear structure effect for the fully differential electron impact ionization cross sections of H2 and He measured in the perpendicular plan where the two outgoing electrons have equal energies of 10 eV (20eV excess energy). For this case we demonstrated that He had a maximum for back-to-back scattering and H2 had a minimum due to the different nuclear configurations. We have extended our investigation for H2 to lower excess energies down to 2eV (both final state electrons have 1eV energy). We will show that, as the excess energy decreases, the effective impact parameter increases and molecular cross sections start to look like the atomic ones as the nuclear separation becomes less important.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2007
e, 2e) ionization differential cross sections are presented for incident electron energies ranging from 15 eV to 95 eV above the ionization threshold of the 1b 1 molecular state of H 2 O. Experimental results and theoretical analysis were derived for three energies in a coplanar symmetric geometry, and for three energies in an asymmetric geometry. The experimental data show a wide variation in the cross section over this range of energies, whereas the theoretical analysis carried out using a sophisticated molecular DWBA model, which includes the final state post collision interaction (PCI), shows best agreement at lower energies. The experimental techniques used to collect the data are described here as well as an improved theoretical approach using elastic scattering cross sections to evaluate the accuracy of the distorted waves utilized in the calculation of the ionization cross sections.