Diploma - Max Planck Institute for Solid State Research

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$diffraction from single powder grains - Max Planck Institute for Solid ...$

20 3 Experimental foundations chamber varies in time. For this purpose, especially getter pumps are used because the final pressure of mechanical pumps like turbo pumps is limited by their reverse flow. In laboratories, usually the radiation from electrical discharge lamps (e.g. He) is used, and therefore, in that case, turbo pumps are preferred to getter pumps which are not able to bind noble gases. Commonly, there are at least three ports: a transfer valve to the preparation chamber, the beamline and an analyzer port apart from windows, ports for ion gauges, pumps and other. Below, the different designs and experimental conditions of the two endstations are illustrated. 3.3 BESSYII: 1 3 ARPES The 1 3 ARPES setup (see fig. 3.3b) was constructed to achieve ≤1 meV energy resolution of the beamline as well as of the analyzer at a sample temperature of ≤1 K. Since the latter is restricted by the cooling agent as well as by the thermal isolation and the thermal contact of the sample holder to the cooling reservoir, it was necessary to build a cooling shield combined with a cryostat which is connected to the sample holder. The cooling process is nested using liquid nitrogen for the outer shield, filled with liquid helium inside which surrounds the closed 3 He cooling cycle. A compromise between cooling efficiency and sample orientations’ degrees of freedom was found by allowing only x, y, z and incident angle movements limiting the remaining rotations and hence minimizing the radius of the cryostat. It has one entry (beamline) and one exit (analyzer) slit which are usually open and a sample entrance which is locked by a mechanical-driven flap gate. Principally it is possible to obtain (projected) constant energy surfaces, however this is limited by the precision of the manipulator. Since the size of a homogeneous sample region (meaning same kind of surface atoms, little surface defects and same crystal domain) is very small (in the range of 100 µm 2 ), the accuracy of the manipulator should be as good as possible. Unfortunately, having adapters to steer the sample holder inside which have a rather large play when changing the screwing direction does not allow to stay at the same sample region. The analyzer slit has been mounted vertically. 3.4 SLS: SIS-HRPES This endstation (see fig. 3.3c) is able to achieve around 10 K without the necessity of shielding. Thus one has the advantage of an high precision manipulator with no angular restriction which is fully computer-controlled and hence each position can be approached several times without losing the absolute sample position. Therefore, most of the BZ maps and high-symmetry cuts of the BZ have been obtained here. In contrast to
3.4 SLS: SIS-HRPES 21 1 3 ARPES the analyzer slit is mounted horizontally. Accordingly vertical and horizontal polarized spectra are not directly comparable for both endstations.
Page 1 and 2: - Photoemission on EuRh 2 Si 2 - di
Page 3: Abstract A thorough knowledge of co
Page 7: vii Nomenclature AF APW ARPES BO BZ
Page 10 and 11: 2 1 Introduction conflicting limits
Page 12 and 13: 4 2 Theoretical foundation fore the
Page 14 and 15: 6 2 Theoretical foundation system a
Page 16 and 17: 8 2 Theoretical foundation such a s
Page 18 and 19: 10 2 Theoretical foundation Figure
Page 20 and 21: 12 2 Theoretical foundation Figure
Page 22 and 23: 14 2 Theoretical foundation Fi
Page 25 and 26: 17 3 Experimental foundations 3.1 P
Page 27: 3.2 General setup 19 Figure 3.2: ch
Page 31 and 32: 23 4 EuRh 2 Si 2 - semi-localized e
Page 33 and 34: 4.1 Overview - properties and class
Page 49 and 50: 4.2 Hybridization: localized versus
Page 61 and 62: 4.3 Perspective: quasi-linear dispe
Page 63: 4.3 Perspective: quasi-linear dispe
Page 66 and 67: 58 5 Summary to the f-d interaction
Page 68 and 69: 60 Bibliography [13] B. Kramer. A P
Page 70 and 71: 62 Bibliography [44] T. M. Rice and
Page 72 and 73: 64 Bibliography [75] Hari C. Manoha
Page 75: List of Tables 67 List of Tables 2.
Page 79:
Erklärung Hiermit versichere ich,
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Diploma - Max Planck Institute for Solid State Research

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