PHYS07200604007 Manas Kumar Dala - Homi Bhabha National ...

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Experimental Techniques 50 exploration of matter. Synchrotron radiation are produced when charge particles Figure 2.17: Schematic of the synchrotron radiation. moving with relativistic velocity are deflected in a magnetic field. The synchrotron radiation had been developed by taking the effect of Heinrich Hetz [1] as the electrons fly around the curves through the magnetic field emit electromagnetic radiation. In SR facilities the accelerated electrons fly in a closed orbit inside a stainless steel tube, which consists of large electromagnets at regular intervals to guide the electrons around the curves and keep them focussed in the center of the tube called the storage ring. The electrons are generated in an injection system consisting of an electron source and an accelerator, either a synchrotron or a linear accelerator. When the electrons are accelerated to the operating energy of the storage ring, they are injected into the storage ring. The bending magnets are used to deflect the electron beam. In order to compensate the energy loss of the electrons during the SR emission, the electrons are accelerated each time as they pass through the RF cavity installed inside the storage ring. A schematic of SR light source is shown in the Fig. 2.17. In the developed synchrotrons the intensity of the emitted radiation is enhanced by insertion devices (undulator or wiggler). The insertion devices are periodic arrays of permanent magnets. When electrons traverse in the periodic array of magnets are forced to undergo oscillations and radiate (Fig. 2.18 shows the schematic representation).The static magnetic field is alternating along the length of the insertion devices with a wave length λ 0 . The radiation produced by insertion devices is very intense and is guided through beam lines for various experiments. An important dimensionless parameter K which characterizes the nature of electron motion is defined as,
Experimental Techniques 51 Figure 2.18: Schematic representation of an insertion device. K = eB 0λ 0 (2.40) 2πmc where e is the electronic charge, B 0 is the magnetic field, m is the electron rest mass and c is the speed of light. For undulator K > 1, the oscillation amplitude is bigger and the radiation contributions from each field period sum up independently leading to a broad energy spectrum. Insertion devices can provide several orders of magnitude higher flux than a simple bending magnet and are in high demand at synchrotron radiation facilities. For an undulator with N periods, the brightness can be up to N 2 more than a bending magnet. The experiments presented in this thesis were performed at different synchrotrons using monochromators of various type. The HRPES and XAS experiments were performed at the WERA soft x-ray beamline of ANKA synchrotron, Germany. At BEAR and BACH beamlines of ELETTRA synchrotron, Italy, the XAS experiments were performed. At WERA soft x-ray beamline of ANKA synchrotron, a spherical grating monochromator (DRAGON type) [21, 52] was used. The layout of the WERA soft x-ray beamline is shown in the Fig. 2.19. It consists of a pair of mirrors 1 (horizontal) and
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SPECTROSCOPIC INVESTIGATIONS OF THE
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iii To My Parents
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Maharana, P. Khare, D. K. Basa, K.
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List of Publications/Preprints [1]
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Synopsis The perovskite type mangan
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to the t 2g and e g spin-up states
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Bibliography [1] R. von Helmolt, J.
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Contents CERTIFICATE Acknowledgemen
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List of Figures 1.1 Temperature dep
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2.2 Schematic view of the energetic
Page 21 and 22: 3.4 O K edge x-ray absorption spect
Page 23 and 24: Chapter 1 Introduction 1
Page 25 and 26: Introduction 3 The temperature and
Page 27 and 28: Introduction 5 Figure 1.2: Schemati
Page 29 and 30: Introduction 7 Figure 1.4: A schema
Page 31 and 32: Introduction 9 Figure 1.6: Schemati
Page 33 and 34: Introduction 11 Figure 1.8: Differe
Page 35 and 36: Introduction 13 Figure 1.10: A sche
Page 37 and 38: Introduction 15 Figure 1.12: Schema
Page 39 and 40: Introduction 17 Figure 1.13: Phase
Page 41 and 42: Bibliography [1] R. von Helmolt, J.
Page 43 and 44: Introduction 21 [31] Damien Saurel,
Page 45 and 46: Chapter 2 Experimental Techniques 2
Page 47 and 48: Experimental Techniques 25 Figure 2
Page 49 and 50: Experimental Techniques 27 Let us n
Page 51 and 52: Experimental Techniques 29 and G(k,
Page 55 and 56: Experimental Techniques 33 point wi
Page 57 and 58: Experimental Techniques 35 negative
Page 59 and 60: Experimental Techniques 37 ∆E = E
Page 63 and 64: Experimental Techniques 41 ( ) dσ
Page 65 and 66: Experimental Techniques 43 The expe
Page 67 and 68: Experimental Techniques 45 are weld
Page 71: Experimental Techniques 49 Figure 2
Page 77 and 78: Bibliography [1] H. Hertz, Ann. Phy
Page 79 and 80: Experimental Techniques 57 [35] K.
Page 81 and 82: Chapter 3 Electronic Structure of P
Page 83 and 84: Electronic Structure of Pr 0.67 Ca
Page 95 and 96: Bibliography [1] I. G. Deac, J. F.
Page 99 and 100: Chapter 4 Electronic Structure of P
Page 101 and 102: Electronic Structure of Pr 1−x Ca
Page 119 and 120: Electronic Structure of Ca 0.86 Pr
Page 121 and 122: Electronic Structure of Ca 0.86 Pr
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Electronic Structure of Ca 0.86 Pr
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Bibliography [1] C. Zener, Phys. Re
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Summary and Conclusions 109 In this
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