Astronomical Spectroscopy: An Introduction To The Atomic And Molecular Physics Of Astronomical Spectra (2nd Edition)

by Jonathan Tennyson

Overview

Nearly all information about the Universe comes from the study of light as it reaches us. However, understanding the information contained in this light requires both telescopes capable of resolving it into its component colours and a detailed knowledge of the quantum mechanical behaviour of atoms and molecules. This book, which is based on a third-year undergraduate course taught by the author at University College London, presents the basic atomic and molecular physics necessary to understand and interpret astronomical spectra. It explains how and what kind of information can be extracted from these spectra. Contemporary astronomical spectra are used extensively to study the underlying atomic physics and illustrate the results.

Product Details

ISBN-13:	9789814291972
Publisher:	World Scientific Publishing Company, Incorporated
Publication date:	01/25/2011
Edition description:	Older Edition
Pages:	236
Product dimensions:	6.00(w) x 8.90(h) x 0.70(d)

Table of Contents

Preface v

1 Why Record Spectra of Astronomical Objects? 1

1.1 A Historical Introduction 1

1.2 What One Can Learn from Studying Spectra 3

2 The Nature of Spectra 7

2.1 Transitions 7

2.2 Absorption and Emission 8

2.3 Other Measures of Transition Probabilities 10

2.4 Stimulated Emission 10

2.5 Optical Depth 11

2.6 Critical Density 12

2.7 Wavelength or Frequency? 13

2.8 The Electromagnetic Spectrum 14

3 Atomic Hydrogen 17

3.1 Overview 17

3.2 The Schrödinger Equation of Hydrogen-Like Atoms 17

3.3 Reduced Mass 18

3.4 Atomic Units 19

3.5 Wavefunctions for Hydrogen 20

3.6 Energy Levels and Quantum Numbers 21

3.7 H-Atom Discrete Spectra 23

3.8 H-Atom Spectra in Different Locations 29

3.8.1 Balmer series 29

3.8.2 Lyman series 33

3.8.3 Infrared lines 35

3.9 H-Atom Continuum Spectra 35

3.9.1 Processes 35

3.9.2 H-atom emission in H II regions 36

3.10 Radio Recombination Lines 38

3.11 Radio Recombination Lines for Other Atoms 40

3.12 Angular Momentum Coupling in the Hydrogen Atom 43

3.13 The Fine Structure of Hydrogen 44

3.14 Hyperfine Structure in the H Atom 45

3.15 Allowed Transitions 46

3.16 Hydrogen in Nebulae 47

4 Complex Atoms 51

4.1 General Considerations 51

4.2 Central Field Model 52

4.3 Indistinguishable Particles 54

4.4 Electron Configurations 55

4.5 The Periodic Table 56

4.6 Ions 58

4.7 Angular Momentum in Complex Atoms 59

4.7.1 L-S or Russell-Saunders coupling 59

4.7.2 j-j coupling 61

4.7.3 Why two coupling schemes? 61

4.8 Spectroscopic Notation 62

4.9 Parity of the Wavefunction 63

4.10 Terms and Levels in Complex Atoms 64

5 Helium Spectra 69

5.1 He I and He II Spectra 69

5.2 Selection Rules for Complex Atoms 71

5.3 Observing Forbidden Lines 74

5.4 Grotrian Diagrams 75

5.5 Potential Felt by Electrons in Complex Atoms 77

5.6 Emissions of Helium-Like Ions 78

6 Alkali Atoms 81

6.1 Sodium 81

6.2 Spin-Orbit Interactions 84

6.3 Fine Structure Transitions 88

6.4 Astronomical Sodium Spectra 89

6.5 Other Alkali Metal-Like Spectra 93

7 Spectra of Nebulae 99

7.1 Nebulium 100

7.2 The Bowen Mechanism 104

7.3 Two Valence Electrons 107

7.4 Autoionisation and Recombination 109

8 Spectra in Magnetic Fields 115

8.1 Uniform Magnetic Field 116

8.2 Strong Magnetic Field 117

8.3 Weak Magnetic Field 118

8.3.1 The normal Zeeman effect 118

8.3.2 The anomolous Zeeman effect 119

8.4 Spectra in Magnetic Field 120

9 X-Ray Spectra 123

9.1 Inner Shell Processes 123

9.2 The Solar Corona 127

9.3 The Structure of Highly Ionised Atoms 127

9.4 Isotope Effects 131

10 Molecular Structure 135

10.1 The Born-Oppenheimer Approximation 136

10.2 Electronic Structure of Diatomics 137

10.2.1 Labelling of electronic states 140

10.2.2 Symmetry 141

10.2.3 State labels 143

10.3 Schrödinger Equation 144

10.3.1 Nuclear motion in diatomic molecules 144

10.4 Fractionation 149

10.5 Vibration-Rotation Energy Levels 150

10.6 Temperature Effects 152

10.6.1 Rotational state populations 152

10.6.2 Vibrational state populations 154

10.6.3 Electronic state populations 155

11 Rotational Spectra 157

11.1 Rotational Structure of Polyatomic Molecules 157

11.2 Selection Rules: Pure Rotational Transitions 160

11.3 Selection Rules 161

11.4 Isotope Effects 166

11.5 Rotational Spectra of Other Molecules 166

11.6 Rotational Spectra of Molecular Hydrogen 170

11.7 Maser Emissions 170

12 Vibration-Rotation Spectra 175

12.1 Vibrations in Polyatomic Molecules 175

12.2 Vibrational Transitions 177

12.2.1 Structure of the spectrum 178

12.2.2 Isotope effects 181

12.2.3 Hydrogen molecule vibrational spectra 181

12.3 Astronomical Spectra 183

13 Electronic Spectra of Diatomic Molecules 187

13.1 Electronic Transitions 187

13.2 Selection Rules 188

13.2.1 Vibrational selection rules 189

13.2.2 Rotational selection rules 190

13.3 Transition Frequencies 192

13.4 Astronomical Spectra 193

13.5 Non-¹ Σ Electronic States 195

Solutions to Model Problems 199

Further Reading and Bibliography 215

Index 217