Model for the production of circular polarization via beam-foil interaction

Schröder, Heinz C.; Kupfer, E.

doi:10.1007/bf01409085

Cited by 101 publications

(30 citation statements)

References 14 publications

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“…A phenomenological explanation is given by the densitygradient model of Schröder and Kupfer. 36 After depositing Co on the Cu(111) substrate, we obtained a magnetic signal from the surface. This magnetic signal can be detected either in remanence or as a function of the outer magnetic field.…”

Section: Resultsmentioning

confidence: 99%

Thin Co films on Cu(111) studied by electron capture spectroscopy

Schleberger¹,

Manske²,

Dirska³

2005

Surface & Interface Analysis

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We have studied thin films of Co on Cu(111) single crystals with electron capture spectroscopy (ECS). The magnetism from the cobalt layer can be detected clearly in remanence and as a function of the outer magnetic field. The measured circular polarization of the emitted light is related directly to the structural and magnetic changes of the system, depending on the cobalt layer thickness. We find the set-in of in-plane magnetization at ∼2 monolayers of cobalt and the saturation of our signal at a film thickness of 7-8 monolayers. At coverages above 3-4 monolayers the increasing growth of hcp cobalt domains at the expense of fcc cobalt domains gives rise to a linearly increasing ECS signal up to 7.5 monolayers. We attribute this to the fact that the fcc cobalt domains are covered with copper, whereas the hcp cobalt domains expose cobalt in the upper layer. Monte-Carlo simulations of our ion scattering experiments show that great experimental care has to be taken in order to avoid excessive sputtering damage to the sample. By using moderate primary ion energies and small angles of incidence, thin films can be investigated with ECS in the grazing incidence geometry without changing the film structure.

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Section: Resultsmentioning

confidence: 99%

Thin Co films on Cu(111) studied by electron capture spectroscopy

Schleberger¹,

Manske²,

Dirska³

2005

Surface & Interface Analysis

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“…As a consequence S should be reduced and C correspondingly increased. This however is not observed: measurements indicate that C is always small [14,3], and a theoretical estimate [7] even gave p2 =0 for grazing incidence. Therefore in the following p~ and the Stark effect will be neglected.…”

Section: Influence Of Electric Fieldsmentioning

confidence: 85%

“…Details of the excitation process are unknown at present. For the related beam foil excitation mechanism a number of crude models [5][6][7] have been proposed, but so far none of them has been proven. In the interpretation of polarized radiation from complex atoms some progress has recently been made.…”

Section: Introductionmentioning

confidence: 99%

Unified description of circular polarization in supermultiplet lines of ions, excited by beam surface interaction

Schröder

1978

Z Physik A

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The excitation process of energetic ions, reflected at grazing angles from a metallic target, is assumed to be an electron-loss-capture-sequence. The density operator at the time of the last capture is factorized into an anisotropic part for the optical electron and an isotropic part for the inner electrons. Parentage approximation and LS-coupling then give the orientation for all levels of a supermultiplet. The circular polarized light, emitted during transitions from these levels, can be well fitted, with exception of lines from L = 0 terms. This shortcoming is removed by an extended model. This suggests that the parent ions, too, are oriented.

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“…and Kupfer [20] pointed out that the alignment decreases monotonically by ,,~10% from l/v=0 to 1/v=0.3 ns/mm. Since the calculations are based on the assumption of an ideal solid surface, the absolute value of the alignment found in [20] was too high.…”

Section: Next We Discuss the Energy Variation Of The Initial Alignmenmentioning

confidence: 97%

Influence of surface electric fields on the alignment of the hydrogen-2p state after beam-foil-excitation

Kupfer

Winter

1978

Z Physik A

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In contrast to other atomic systems, foil excited hydrogen or hydrogen-like atoms show a negative alignment for various energy ranges. We suggest that this particular behaviour results from the degeneracy of different L states in hydrogenic systems and an observable influence of a surface electric field modifying the initial alignment via Stark effect. L IntroductionThe beam-foil interaction process produces a difference in the magnetic sublevel populations of the excited states. This population asymmetry can be observed by the radiation emitted in transitions from excited states. If a foil is oriented perpendicular to the beam axis, axial and reflection symmetry with respect to this axis hold and only linear polarization is measured. From these measurements one determines the alignment (Po-o -P~a)/(Vao + Pal) of an excited p state, where the density matrix element %M,~ is proportional to the cross section for the formation of a state [nLML).As a particular result the alignment of the beam-foil excited states of hydrogen [1][2][3] and of hydrogen-like ions [4] is negative over a wide energy range in contrast to non-hydrogenic systems, for which always positive alignment [5] is found. We use the assumption of Eck [6] and Lombardi [7] that a strong electric field exists at the surface of a carbon foil in order to explain the particular behaviour ofhydrogenic systems. Their energy levels are strongly affected by an electric field, which may cause the alignment to change sign as will be shown below. II. Theoretical ModelIn the present work we discuss the alignment of a hydrogen-2p state as determined from the polarization * This work is part of the research program of the "Sonderforschungsbereich 161" supported by the Deutsche Forschungsgemeinschaft of the Lyman-e radiation emitted perpendicular to the beam. We refer to the following geometry: the beam and the detector axis coincide with the z and y direction, respectively. The foil is located in the x-y-plane. An ensemble of excited ions or atoms leaves the foil at a time t o. Postulating, as is usually done, that the excitation process results from pure electrostatic interactions, the initial density matrix of the excited states factorizes into an isotropic spin and an anisotropic angular momentum matrix (nLML[a(to) In' I2M~).(The angular momentum basis is characterized by n, the principal quantum number, L, the angular momentum, and ML, the corresponding magnetic quantum number with respect to the z direction as quantization axis). We recall that the hermiticity of a(to)From symmetry of reflection at the x-z-plane follows (lb) and axial symmetry about the beam direction means (lc)The angular momentum density matrix of the foilexcited hydrogen n=2 state at time t= t o is given by 0340-2193/78/0285/0003/$01.00

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Model for the production of circular polarization via beam-foil interaction

Cited by 101 publications

References 14 publications

Thin Co films on Cu(111) studied by electron capture spectroscopy

Thin Co films on Cu(111) studied by electron capture spectroscopy

Unified description of circular polarization in supermultiplet lines of ions, excited by beam surface interaction

Influence of surface electric fields on the alignment of the hydrogen-2p state after beam-foil-excitation

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