Excitation in low-energy Li+ collisions with cesiated W(110) surfaces: alignment and orientation of the collisionally excited Li(2p) state

Schall, H.; Brenten, H.; Knorr, K.; Kempter, V.

doi:10.1007/bf01437329

Cited by 8 publications

(3 citation statements)

References 19 publications

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“…This behavior is similar to that obtained using K overlayers, and is similar to the behavior observed by Kempter and co-workers for Li ϩ → Cs/W͑110͒. 4,5 We estimate that the peak values of the relative yields correspond to absolute yields of 0.004 Li 0 (2p) atom per incident ion when E i ϭ400 eV, and 0.0003 Li 0 (2p) atom per incident ion when E i ϭ100 eV.…”

Section: Datasupporting

confidence: 89%

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Charge transfer in hyperthermal energy collisions ofLi+with alkali-metal-covered Cu(001). II. Dynamics of excited-state formation

et al. 1996

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We have measured the relative probability of excited state ͓Li 0 (2p)͔ formation versus the work-function change induced by alkali-metal adsorbates when hyperthermal energy Li ϩ ions are incident on alkali-metalcovered Cu͑001͒. This probability is broadly peaked as the work function decreases, and decreases by approximately an order of magnitude when the velocity of the ions in the incident beam is decreased from 1.05ϫ10 5 to 0.52ϫ10 5 m s Ϫ1 , and the incident angle is i ϭ65°as measured from the surface normal. Theoretical calculations based on a many-body solution to the time-dependent Anderson-Newns model of charge transfer ͑discussed in the preceding paper͒ qualitatively reproduce the observed trends. These calculations suggest that the peak in the excited-state probability results mainly from two effects: first, the decreasing difference between the energy of the Li 0 (2p) state and the Fermi level as the work function decreases, which tends to increase the excited-state probability; and second, the competition of the Li 0 (2p) state with the Li Ϫ (2s 2 ) negative ion state at low work functions, which tends to decrease the excited-state probability. Differences between the Li 0 (2s) and Li 0 (2p) lifetimes also play a role in the formation of the peak, as does electron-hole pair production.

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Section: Datasupporting

confidence: 89%

“…4,5,37 The mechanism proposed for the peak observed in that system is as follows. 4,37 First, an electron from the surface is resonantly transferred into the Li 0 (2p) state of the atom during the approach of the incoming ion to the surface.…”

Section: Alternative Explanation Of the Nonmonotonic Behavior Of P 0 mentioning

confidence: 99%

Charge transfer in hyperthermal energy collisions ofLi+with alkali-metal-covered Cu(001). II. Dynamics of excited-state formation

et al. 1996

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“…There is provocative theoretical 43 work on Auger processes which we can draw upon to find sensible models for the amplitudes. In addition, experiments have found secondary electrons resulting from ionsurface collisions which are consistent with various Auger processes, 44,35,37 but the determination of absolute cross sections is a difficult experimental problem. The Auger term complicates the solution of the many-body equations significantly because it involves three momenta indices.…”

Section: Dissipation Due To the Formation Of Particle Hole Pairsmentioning

confidence: 99%

Many-body theory of charge transfer in hyperthermal atomic scattering

et al. 1993

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We use the Newns-Anderson Hamiltonian to describe many-body electronic processes that occur when hyperthermal alkali atoms scatter off metallic surfaces.Following Brako and Newns, we expand the electronic many-body wavefunction in the number of particle-hole pairs (we keep terms up to and including a single particle-hole pair). We extend their earlier work by including level crossings, excited neutrals and negative ions. The full set of equations of motion are integrated numerically, without further approximations, to obtain the many-body amplitudes as a function of time. The velocity and work-function dependence of final state quantities such as the distribution of ion charges and excited atomic occupancies are compared with experiment. In particular, experiments that scatter alkali ions off clean Cu(001) surfaces in the energy range 5 to 1600 eV constrain the theory quantitatively. The neutralization probability of Na + ions shows a minimum at intermediate velocity in agreement with the theory. This behavior contrasts with that of K + , which shows virtually no neutralization, and with Li + , which exhibits a monotonically increasing neutral fraction with decreasing velocity. Particle-hole excitations are left behind in the metal during a fraction of the collision events; this dissipated energy is predicted to be quite small (on the order of tenths of an electron volt). Indeed, classical trajectory simulations of the surface dynamics account well for the observed energy loss, and thus provide some justification for our truncation of the equations of motion at the single particle-hole pair level. Li + scattering experiments off low work-function surfaces provide qualitative information on the importance of many-body effects. At sufficiently low work function, the negative ions predicted to occur are in fact observed. Excited neutral Li atoms (observed via the optical 2p → 2s transition) also emerge from the collision. A peak in the calculated Li(2p) → Li(2s) photon intensity occurs at intermediate work function in accordance with measurements.

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Li+ neutralisation in back-scattering from alkali/Al(100) surfaces: comparison between the various alkalis

et al. 1998

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Excitation in low-energy Li+ collisions with cesiated W(110) surfaces: alignment and orientation of the collisionally excited Li(2p) state

Cited by 8 publications

References 19 publications

Charge transfer in hyperthermal energy collisions ofLi+with alkali-metal-covered Cu(001). II. Dynamics of excited-state formation

Charge transfer in hyperthermal energy collisions ofLi+with alkali-metal-covered Cu(001). II. Dynamics of excited-state formation

Many-body theory of charge transfer in hyperthermal atomic scattering

Li+ neutralisation in back-scattering from alkali/Al(100) surfaces: comparison between the various alkalis

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