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Duncan, M. M.; Menendez, M. G.

doi:10.1103/physreva.23.1085

Cited by 19 publications

(9 citation statements)

References 12 publications

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“…Their semiclassical binary encounter model proposed that projectile electrons were elastically scattered by the target in a way closely resembling the scattering of free electrons (Bohr 1948). Hartley and Walters (i987bj have pointed out that the singiy difierentiai cross section for the eiastic scattering of free electrons and for Burchs elastic scattering model (ESM) both show similar structure in the angular dependence (Duncan andMenendez 1979, 1981, Heil et a/ 1991d); this structure arising from the ability of the projectile electrons to probe successive shells of the target. It is particularly easy to see the operation of the ESM for 180' scattering.…”

Section: Introductionmentioning

confidence: 99%

The doubly inelastic contribution to electron loss: H⁰and He⁰(0.5 MeV u^-1) in collision with Ar

Kuzel¹,

Heil²,

Maier³

et al. 1992

J. Phys. B: At. Mol. Opt. Phys.

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Section: Introductionmentioning

confidence: 99%

The doubly inelastic contribution to electron loss: H⁰and He⁰(0.5 MeV u^-1) in collision with Ar

Kuzel¹,

Heil²,

Maier³

et al. 1992

J. Phys. B: At. Mol. Opt. Phys.

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“…Somewhat surprisingly, subsequent measurements of doubly differential electron loss cross sections from hydrogen or helium impact on all rare gases up to Kr [12][13][14] did not reveal any Ramsauer-Townsend effects on the electron loss peak itself. Both peak position and peak width were found to depend smoothly on the ejection angle within the experimental errors, thereby throwing some doubt on any theory derived from free electron scattering.…”

Section: Ramsauer-townsend Effect In the Electron Loss From H° Collidmentioning

confidence: 91%

“…Second, the backward hemisphere was only explored with He, Ne, and Ar targets [13][14][15] and at such high collision velocities that Ramsauer-Townsend effects are either absent (He, Ne) or rather weak (Ar). The heaviest target used so far for electron loss peak shape studies [12] was Kr, but only at emission angles below 20°, and at these forward angles the strong decrease of the electron loss peak intensity with angle veils any contingent structures in the doubly differential cross section.Our experiment has been designed to overcome these shortcomings. By using hydrogen projectiles we were able to suppress the smooth background from target ionization in the electron loss peak region to less than 10%, even in a noncoincident experiment.…”

mentioning

confidence: 99%

Ramsauer-Townsend effect in the electron loss fromH0colliding with heavy atoms

et al. 1993

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The emission pattern of loosely bound projectile electrons is strongly dependent on the target species. For 0.5 MeV hydrogen colliding with krypton we observe large variations in the intensity of these electrons as a function of emission angle. There are also large changes in the energy and width of the electron loss peak associated with these intensity variations. These features are closely related to the Ramsauer-Townsend scattering of free electrons and can be interpreted within the electron impact approximation, a model which successfully combines free electron scattering by the heavy target with the Compton profile of the initially bound projectile electron.PACS numbers: 34.50.FaOne of the fundamental processes occurring in heavy ion collisions is the ejection of electrons. A study of their energy and angular distribution provides a unique insight into the collision dynamics and into the atomic structure of the collision partners [1]. With the availability of recent more accurate measurements one has a sensitive test of traditional theoretical models and those being newly developed. An essential feature in the spectrum arising from projectiles which carry electrons into the collision is in "the electron loss peak" which was independently discovered by Burch, Wieman, and Ingalls [2] and Wilson and Toburen [3] and identified to originate from these projectile electrons. Since the peak is located at an energy which approximately corresponds to the energy of the outermost projectile electron in the target rest frame, one of the earliest interpretations was based on the idea that electron loss might be treated as an elastic collision between the projectile electron and the target atom. Free electron-atom scattering (as reviewed by, e.g., Bransden and McDowell [4]) is a field which has been thoroughly investigated in order to get detailed information about the electronic properties of the target. As early as the 1920s, Ramsauer [5] and Townsend and Bailey [6] discovered pronounced structures in the energy dependence of the elastic scattering cross section from heavy rare gas atoms. Later investigations [7,8] have revealed that these intensity variations arise from deep minima in the angular dependent differential cross sections. These structures, which can be reproduced with the help of close-coupling calculations [9,10], have been interpreted in terms of interference effects between the different partial waves contributing to the scattering amplitude. The absence of structures for helium targets and the increase of the number of minima with increasingly heavier rare gases (at fixed impact energy) could then readily be explained by the number of partial waves required: only a few for He, but some tens for the heaviest gases.Menendez and Duncan [11] were the first to discover structures in the angular dependent singly differential cross section in the case of clothed ion impact. Somewhat surprisingly, subsequent measurements of doubly differential electron loss cross sections from hydrogen or helium impact on all ...

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“…This is also revealed by measurements of the peak energy of the ELP [3]: The energy changes from Eem=lV 2 at 0~-0 ~ (a result of the IVe--V1-1 singularity of the cross section) to Eem=lv2-e i for angles 0>30 ~ This value is predicted by the impulse approximation which yields (1) [1]. An electron emission spectrum at 173 ~ for 0.5 MeV H on Ar by Duncan and Menendez [8] is well described by a hydrogenic CP on the high electron energy side but deviates on the low energy side: the spectrum exhibits a rather strong asymmetry (see also ref. [9]).…”

Section: (Dcr)mentioning

confidence: 92%

“…The experimental data favor the molecular model, though one has to keep in mind that the data might be rather uncertain especially at large p~-values (which correspond to large electron energies Ee) due to problems of background subtraction. We have applied our analysis to data of Duncan and Menendez [8] for H-, H~ and H + on Kr also. These data have been obtained in the angular range 5 ~ 10 ~ It turns out that the experimental width of the ELP at these angles is remarkably smaller than the corresponding CP's.…”

Section: (Dcr)mentioning

confidence: 99%

Molecular compton profiles from inelastic atom-electron scattering

Bell

1984

Z Physik A

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Recent measurements of the electron loss peak from H~-ions impinging on Ar have been analyzed in terms of projectile Compton profiles (CP). It is shown that projected momentum distributions, i.e. CP's, can be determined for the molecular ion H~-.Recently it has been demonstrated that Compton profiles (CP), i.e. projected electron momentum distributions, of either target atoms or projectile ions can be obtained by inelastic ion-electron scattering [1]. It is the aim of this paper to show that existing data of electron loss measurements are sensitive enough to extract the Compton profile of H~-molecules. (For a recent review of molecular Compton profiles see [2].) We have analyzed the electron loss peak (ELP) measurements of K6v6r et al. [3] for H~--Ar and He +-Ar collisions in terms of CP's. If the collision velocity v is much larger than the initial orbital velocity v~ of the scattered electrons, the double differential cross section (DDCS) for the emission of projectile electrons can be factorized [1] :Here, (da/df2)e is the elastic cross section for scattering an electron with velocity v at a screened target nucleus and Jp(p=) the CP of the projectile:O~(p) is the initial electron wave-function, E e the electron lab energy and Eem the electron energy at which the electron loss peak occurs (atomic units are used). The essential feature of (1) is that the DDCS factorizes into a cross section which contains all the information of the electron-atom interaction and which is essentially constant in the region of the ELP and a CP which is characteristic of the electron's initial state. For the evaluation of (1) where N is a normalization constant. Putting (4) into (2) yields a directional CP which has to be averaged over all angles between the momentum component p~ (which is parallel to the beam direction) and the bond direction /~ assuming an isotropic distribution of/~ with respect to $ [7]. Figure 1 shows the comparison of experimental data of [3] for 0.8 MeV/amu He + (circles), 0.8 MeV/ amu H~-(closed triangles) and 1.995 MeV/

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Some similarities and differences in collisional electron loss ofH−,H2+

Cited by 19 publications

References 12 publications

The doubly inelastic contribution to electron loss: H⁰and He⁰(0.5 MeV u^-1) in collision with Ar

The doubly inelastic contribution to electron loss: H⁰and He⁰(0.5 MeV u^-1) in collision with Ar

Ramsauer-Townsend effect in the electron loss fromH0colliding with heavy atoms

Molecular compton profiles from inelastic atom-electron scattering

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Some similarities and differences in collisional electron loss ofH−,H2+

Cited by 19 publications

References 12 publications

The doubly inelastic contribution to electron loss: H0and He0(0.5 MeV u-1) in collision with Ar

The doubly inelastic contribution to electron loss: H0and He0(0.5 MeV u-1) in collision with Ar

Ramsauer-Townsend effect in the electron loss fromH0colliding with heavy atoms

Molecular compton profiles from inelastic atom-electron scattering

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Product

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The doubly inelastic contribution to electron loss: H⁰and He⁰(0.5 MeV u^-1) in collision with Ar

The doubly inelastic contribution to electron loss: H⁰and He⁰(0.5 MeV u^-1) in collision with Ar