New interpretation of Penning spectra from alkali-metal atoms chemisorbed on metal surfaces

Hemmen, R.; Conrad, H.

doi:10.1103/physrevlett.67.1314

Cited by 117 publications

(56 citation statements)

References 21 publications

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“…This (He*)-atom decays via an autodetachment process under emission of an electron which shows up as a strong peak in the Penning spectrum [14]. In this paper we present additional experimental evidence for this interpretation by discussing the low and high coverages of alkali metals in connection with the distance dependence of the various processes which a metastable rare gas atom can undergo during interaction with a low work function surface.…”

Section: Pacsmentioning

confidence: 92%

Inelastic processes in the scattering of metastable rare gas atoms at metal surfaces

Hemmen

Conrad

1992

Appl. Phys. A

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Abstract. Electron spectra of various metastable rare gas atoms systematically measured on a P t ( l l l ) surface with Rb coverages ranging from submonolayers (3%) to multilayers are presented. The different decay channels of the excited particles are discussed in terms of resonant electron exchange processes between the substrate and the projectile in relation to the work function. It is shown that below a certain value of the work function a highly excited negative rare gas atom is formed which can undergo different deexcitation processes. A careful discussion of the branching ratios into the decay channels offers a natural explanation of the variations in the electron spectra induced by alkali metal adsorption. Additionally, an attempt is made to extract information about the alkali metal chemisorption state from the observed electron spectra. 79.20.Ne, 79.80.÷w The practicability of Penning spectroscopy as a technique for surface investigations has been demonstrated in the past by several groups [1][2][3][4][5][6][7]. Penning spectroscopy has been used in studies of adsorbed molecules on transition metals [1][2][3], as well as of molecular crystals [4,5] and alkali halides [6,7] as a method which is complementary to UV photoelectron spectroscopy but has the advantage of strongly enhanced surface sensitivity. The majority of investigations, however, has dealt with studies of alkali metal adsorption, a fact reflecting the essential drawback of the method, namely the existence of a competing process. This resonance ionization transition (RI) occurs predominantly at clean metal surfaces and leads to the formation of He* ions. Only for metallic substrates with a low enough work function to inhibit RI does the Penning transition dominate and produce intense, clear structures in the electron spectrum, comparable to UPS results. PACS:The electron spectra produced by impact of metastable rare gas atoms on clean transition metals (work function typically between 4 and 6 eV) are due to an ion neutralization process (IN) following RI and the resulting electron distributions have to be deconvoluted numerically to extract information about the surface density of states [8]. If the work function is lowered by alkali metal adsorption, sharp structures appear in the spectrum at the Fermi level which are clearly induced by Penning transitions [9-1 t]. The intensity of these peaks has previously been correlated with the alkali induced density of states at E F although the peak intensity strongly increases at intermediate coverages. A further difficulty in the interpretation of Penning spectra is connected to the fact that two He* species (1S and 3S), with an excitation energy difference of 0.8 eV, exist and that the conversion of 1S ~ 3S is very effective [12,13]. As a consequence, the spectra display double peak structures with the respective intensities not being representative of the composition of the incoming metastable beam.In a previous paper, we presented a new interpretation of the sudden appearance of the narrow p...

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Section: Pacsmentioning

confidence: 92%

Inelastic processes in the scattering of metastable rare gas atoms at metal surfaces

Hemmen

Conrad

1992

Appl. Phys. A

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“…(3) For work functions below ¾2.2 eV and a high electron density just below the E F the probability for resonant electron transfer from the surface to He Ł becomes sizeable, forming He Ł 1s 2s 2 ions in front of the surface. 22 These species decay rapidly in an intra-atomic autodetachment process.…”

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confidence: 99%

Study of the electronic and atomic structure of thermally treated SrTiO₃(110) surfaces

Gunhold

Beuermann

Gömann

et al. 2003

Surface & Interface Analysis

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The electronic structure of heated SrTiO 3 (110) surfaces was investigated with metastable impact electron spectroscopy and ultraviolet photoelectron spectroscopy (He(I)). Scanning tunnelling microscopy and atomic force microscopy (AFM) were used to study the topology of the surface. The crystals were heated up to 1000• C under reducing conditions in ultrahigh vacuum or under oxidizing conditions in synthetic air for 1 h, respectively. Under both conditions microfacetting of the surface is observed. The experimental results are compared with ab initio Hartree-Fock calculations, also presented here, carried out for both ideal and reconstructed SrTiO 3 (110) surfaces. The results give direct evidence for Ti termination of the faceted TiO 2 rows.

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“…In particular, it often occurs as an intermediate step in reactions at surfaces (desorption, fragmentation of adsorbates, chemical reactions, quenching of metastable species, etc.) [1][2][3][4]. The one-electron transfer between energetically degenerate electronic levels of the atom and the solid is called the Resonant Charge Transfer (RCT) process.…”

Section: Introductionmentioning

confidence: 99%

Wave packet propagation study of the charge transfer interaction in the F−–Cu(111) and –Ag(111) systems

2001

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The electron transfer between an F − ion and Cu(111) and Ag(111) surfaces is studied by the wave packet propagation method in order to determine specifics of the charge transfer interaction between the negative ion and the metal surface due to the projected band gap. A new modeling of the F − ion is developed that allows one to take into account the six quasiequivalent electrons of F − which are a priori active in the charge transfer process. The new model invokes methods of constrained quantum dynamics. The six-electron problem is transformed to two one-electron problems linked via a constraint. The projection method is used to develop a wave packet propagation subject to the modeling constraint. The characteristics (energy and width) of the ion F − ion level interacting with the two surfaces are determined and discussed in connection with the surface projected band gap.

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New interpretation of Penning spectra from alkali-metal atoms chemisorbed on metal surfaces

Cited by 117 publications

References 21 publications

Inelastic processes in the scattering of metastable rare gas atoms at metal surfaces

Inelastic processes in the scattering of metastable rare gas atoms at metal surfaces

Study of the electronic and atomic structure of thermally treated SrTiO₃(110) surfaces

Wave packet propagation study of the charge transfer interaction in the F−–Cu(111) and –Ag(111) systems

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New interpretation of Penning spectra from alkali-metal atoms chemisorbed on metal surfaces

Cited by 117 publications

References 21 publications

Inelastic processes in the scattering of metastable rare gas atoms at metal surfaces

Inelastic processes in the scattering of metastable rare gas atoms at metal surfaces

Study of the electronic and atomic structure of thermally treated SrTiO3(110) surfaces

Wave packet propagation study of the charge transfer interaction in the F−–Cu(111) and –Ag(111) systems

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Study of the electronic and atomic structure of thermally treated SrTiO₃(110) surfaces