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Optical Astronomical Spectroscopy

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Optical Astronomical Spectroscopy Optical Astronomical Spectroscopy C R Kitchin University of Hertfordshire Institute of Physics Publishing Bristol and Philadelphia Contents Preface xi PART 1 Atomic Processes 1 Introduction to Spectroscopy 1 1.1 Historical background 1 1.2 Types of spectroscopy 8 2 The Physics of Atoms and Molecules 14 2.1 Sommerfeld's refinements 17 2.2 Space quantization 20 2.3 Atomic structure 21 2.4 Other viewpoints 23 2.5 Quantum/wave mechanics 25 Atomic Energy Levels 28 3.1 Multiple electron atoms 29 3.2 L-S coupling 32 3.3 Space quantization 37 3.4 Term formation 37 3.5 Closed shells and subshells 39 3.6 Notation 39 3.7 Hyperfine structure 44 Transitions 46 4.1 Basics 46 4.2 Selection rules 48 4.3 Transition probabilities 53 4.4 Absorption and emission coefficients 57 4.5 Ionization and recombination 64 4.6 X-ray spectra 66 Spectra of Molecules 68 5.1 Introduction 68 5.2 Rotational transitions 70 5.3 Vibrational transitions 76 vn viii CONTENTS 5.4 Electronic transitions 84 6 Radiation in the Presence of Fields 91 6.1 Zeeman effect 91 6.2 Stark effect 91 6.3 Free-free radiation 96 6.4 Synchrotron and gyrosynchrotron radiation 101 6.5 Cerenkov radiation 110 6.6 The Faraday effect 110 7 Spectroscopy of Solid Materials 113 PART 2 Astronomical Spectroscopic Techniques 8 Optical Spectroscopes 119 8.1 Introduction 119 8.2 Diffraction gratings 120 8.3 Grating problems 129 8.4 Diffraction grating spectroscopes 133 8.5 Prisms 143 8.6 Prism spectroscopes 145 8.7 Fourier transform spectroscope (Michelson interferometer) 147 8.8 Fabry-Perot etalons 151 Specialized Optical Spectroscopic Techniques for Astronomy 156 9.1 Introduction 156 9.2 Detectors 156 9.3 Guiding 157 9.4 Widening 158 9.5 Image dissectors 159 9.6 Dekkers 159 9.7 Long slit spectroscopy 160 9.8 Comparison spectra 160 9.9 Flexure 165 9.10 Temperature 165 9.11 Exposures 166 10 Examples of Optical Spectroscopes 168 10.1 Introduction 168 10.2 A small basic spectroscope 168 10.3 A conventional Cassegrain spectroscope 169 10.4 Transmission grating spectroscopes 170 10.5 Coude' spectroscopes 172 10.6 A GRISM-based spectroscope 173 10.7 Multi-obiect SDectroscooes 174 CONTENTS ix 10.8 An echelle grating spectroscope 176 10.9 Infrared spectroscopes 178 10.10 Spacecraft-borne spectroscopes 179 10.11 Fabry-Perot spectroscopes 180 10.12 Fourier transform spectroscopes 182 10.13 Objective prism spectroscopes 184 10.14 The future 185 PART 3 Spectroscopy of Astronomical Sources 11 Spectral Classification 189 11.1 Spectral class 189 11.2 The non-core classes 195 11.3 The luminosity class 198 12 Radial Velocities 202 12.1 Introduction 202 12.2 Traditional approach to radial velocity determination 203 12.3 Objective prism spectra 207 12.4 Machine-readable spectra 208 12.5 Griffin's method 208 12.6 Line identification 208 13 Spectrophotometry 212 13.1 Introduction 212 13.2 Spectral calibration 212 13.3 Photometric calibration 213 13.4 Line strengths 214 13.5 Line broadening 214 13.6 Pressure broadening 215 13.7 Doppler broadening 216 13.8 Magnetic fields 225 13.9 Other effects 225 14 Stars 227 14.1 Introduction 227 14.2 Distance 227 14.3 Temperature 229 14.4 Element abundances 230 14.5 Variable stars 232 14.6 The Sun 235 15 Planets and other Minor Bodies of the Solar System 238 15.1 Introduction 238 15.2 Planetary atmospheres and comets 239 x CONTENTS 15.3 Planetary surfaces 240 15.4 Rotation 241 16 Nebulae and the Interstellar Medium 242 16.1 Nebulae 242 16.2 The interstellar medium 247 17 Extra-Galactic Objects 248 17.1 Introduction 248 17.2 Distances 248 17.3 Spectra 249 17.4 Ages 250 17.5 Sizes 250 17.6 Background radiation 252 Appendices A Conversion Formulae 253 B Term Formation of Equivalent Electrons 254 C Bibliography 256 General 256 History of spectroscopy 256 Quantum mechanics 256 Equipment and techniques 256 Remote sensing 257 Astrophysics 257 Astronomical spectroscopy 258 Atomic spectroscopy 258 Molecular spectroscopy 259 Atomic energy levels and transition probabilities 259 D Constants 261 Index 262.
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