Interference between resonant and Auger mechanisms for charge-exchange processes near surfaces

García, Evelina A.; Wang, N.P.; Monreal, R.; Goldberg, E. C.

doi:10.1103/physrevb.67.205426

Cited by 20 publications

(16 citation statements)

References 29 publications

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“…Early quantum mechanical calculations gave AN transition rates [1] which were several orders of magnitude smaller than those derived from experimental data [2][3][4]. This discrepancy between theory and experiment, however, could not be removed by more recent and sophisticated calculations focusing on the model system He-Al (simple electronic structure, no contributions from RN [5]) [4][5][6][7][8][9][10][11][12][13].…”

mentioning

confidence: 64%

Energy shift of He groundstate close to an aluminum surface

Wethekam

Winter

2005

Surface Science

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mentioning

confidence: 64%

Energy shift of He groundstate close to an aluminum surface

Wethekam

Winter

2005

Surface Science

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“…Then, resonant and Auger mechanisms operating at very different regions of distances to the surface can be treated as independent processes [16]. Otherwise, if it is expected interferences, both mechanisms must be included together in the time-dependent evolution of the charge-transfer process [17,18,29].…”

Section: Introductionmentioning

confidence: 99%

“…In this work, we focus our attention in the collision of positive helium ions with a surface of aluminum, a system which has been widely studied but that still presents many interesting interrogates [14,17,18,22,[30][31][32][33][34][35]. This collisional system was initially considered the perfect one for thinking in neutralization by an Auger mechanism [26], due to the relative position of the He ionization potential (24.6 eV) compared with the aluminum work function (4.43 eV).…”

Section: Introductionmentioning

confidence: 99%

Importance of considering helium excited states inHe+scattering by an aluminum surface

2014

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The He + /Al system is a very interesting projectile-surface combination which was thought initially as an example of a pure Auger neutralization mechanism. Then, because of the measured reionization explained by the antibonding interaction of the projectile state with the core target states, the resonant charge exchange with the band states was considered as another important contribution to the neutralization. Nevertheless, by only considering the neutralization to the ground state of helium, the measured ion survival probability is still overestimated. On the other hand, measurements of electron emission from an Al surface bombarded by He positive ions suggested the possibility of occupied excited states of helium due to the ion-surface collision. In this work, we also include the excited states of He within the time-dependent scattering process in which both neutralization mechanisms, resonant and Auger, are simultaneously contemplated. Our starting point is a multiorbital Anderson Hamiltonian projected over the selected space of ground and excited atomic configurations. An extra term related to the Auger mechanism is added to this Hamiltonian. A difference with previous works is that this approach includes the electron spin and, therefore, the spin fluctuation statistics in the charge-exchange process is correctly taken into account. We find a notable improvement in the agreement with the experiments and also that the interference between both mechanisms is not dramatic.

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“…The problem of calculating Auger rates for the deexcitation-neutralization of He ions incident on a metal surface has been widely treated in literature [24][25][26][27][28][29][30][31][32][33]. These works analyze different aspects of the Auger process for the general case of unpolarized projectiles and nonmagnetic surfaces.…”

Section: Introductionmentioning

confidence: 99%

Spin-dependent screening and Auger neutralization ofHe+ions in metals

2004

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The screening of a He + ion embedded in a paramagnetic electron gas is studied using density functional theory within the local spin density approximation. We calculate the induced electron density and the induced density of states for each spin orientation, parallel and antiparallel to that of the electron bound to the He + ion. Our results show that the screening is preferably due to parallel spin electrons, especially for low electron densities of the medium. In a second step, the rates for Auger neutralization of a He + ion in an electron gas are calculated, paying special attention to their dependence on the spin of the electron excited in the Auger process. The results obtained are used to interpret experiments in which the spin polarization of the emitted yield is measured when a He + projectile is neutralized in front of a metal surface.

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Interference between resonant and Auger mechanisms for charge-exchange processes near surfaces

Cited by 20 publications

References 29 publications

Energy shift of He groundstate close to an aluminum surface

Energy shift of He groundstate close to an aluminum surface

Importance of considering helium excited states inHe+scattering by an aluminum surface

Spin-dependent screening and Auger neutralization ofHe+ions in metals

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