MOLECULES

By JENNIFER SANCHEZ

CONTENTS 1 WHY RECORD SPECTRA OF ASTRONOMICAL OBJECTS? A HISTORICAL INTRODUCTION WHAT ONE CAN LEARN FROM STUDYING SPECTRA 2 THE NATURE OF SPECTRA TRANSITIONS ABSORPTION AND EMISSION OTHER MEASURES OF TRANSITION PROBABILITIES STIMULATED EMISSION OPTICAL DEPTH CRITICAL DENSITY WAVELENGTH OR FREQUENCY? THE ELECTROMAGNETIC SPECTRUM 3 ATOMIC HYDROGEN OVERVIEW THE SCHR¨ODINGER EQUATION OF HYDROGEN-LIKE ATOMS REDUCED MASS ATOMIC UNITS WAVEFUNCTIONS FOR HYDROGEN ENERGY LEVELS AND QUANTUM NUMBERS H-ATOM DISCRETE SPECTRA H-ATOM SPECTRA IN DIFFERENT LOCATIONS BALMER SERIES LYMAN SERIES INFRARED LINES H-ATOM CONTINUUM SPECTRA PROCESSES H-ATOM EMISSION IN H II REGIONS 3 10 RADIO RECOMBINATION LINES 3 11 RADIO RECOMBINATION LINES FOR OTHER ATOMS 3 12 ANGULAR MOMENTUM COUPLING IN THE HYDROGEN ATOM 3 13 THE FINE STRUCTURE OF HYDROGEN 3 14 HYPER?NE STRUCTURE IN THE H ATOM 3 15 ALLOWED TRANSITIONS 3 16 HYDROGEN IN NEBULAE 4 COMPLEX ATOMS GENERAL CONSIDERATIONS CENTRAL FIELD MODEL INDISTINGUISHABLE PARTICLES ELECTRON CON?GURATIONS THE PERIODIC TABLE IONS ANGULAR MOMENTUM IN COMPLEX ATOMS L–S OR RUSSELL–SAUNDERS COUPLING J–J COUPLING WHY TWO COUPLING SCHEMES? SPECTROSCOPIC NOTATION PARITY OF THE WAVEFUNCTION 4 10 TERMS AND LEVELS IN COMPLEX ATOMS 5 HELIUM SPECTRA HE I AND HE II SPECTRA SELECTION RULES FOR COMPLEX ATOMS OBSERVING FORBIDDEN LINES GROTRIAN DIAGRAMS POTENTIAL FELT BY ELECTRONS IN COMPLEX ATOMS EMISSIONS OF HELIUM-LIKE IONS 6 ALKALI ATOMS SODIUM SPIN-ORBIT INTERACTIONS FINE STRUCTURE TRANSITIONS ASTRONOMICAL SODIUM SPECTRA OTHER ALKALI METAL-LIKE SPECTRA 7 SPECTRA OF NEBULAE NEBULIUM THE BOWEN MECHANISM TWO VALENCE ELECTRONS AUTOIONISATION AND RECOMBINATION 8 X-RAY SPECTRA THE SOLAR CORONA ISOTOPE EFFECTS 9 MOLECULAR STRUCTURE THE BORN–OPPENHEIMER APPROXIMATION ELECTRONIC STRUCTURE OF DIATOMICS LABELLING OF ELECTRONIC STATES SYMMETRY STATE LABELS SCHR¨ODINGER EQUATION FRACTIONATION VIBRATION–ROTATION ENERGY LEVELS TEMPERATURE EFFECTS ROTATIONAL STATE POPULATIONS VIBRATIONAL STATE POPULATIONS ELECTRONIC STATE POPULATIONS 10 MOLECULAR SPECTRA 10 1 SELECTION RULES: PURE ROTATIONAL TRANSITIONS 10 1 1 ISOTOPE EFFECTS 10 1 2 ROTATIONAL SPECTRA OF OTHER MOLECULES 10 1 3 ROTATIONAL SPECTRA OF MOLECULAR HYDROGEN 10 2 VIBRATIONAL TRANSITIONS 10 2 1 STRUCTURE OF THE SPECTRUM 10 2 2 ISOTOPE EFFECTS 10 2 3 HYDROGEN MOLECULE VIBRATIONAL SPECTRA 10 3 ELECTRONIC TRANSITIONS 10 3 1 SELECTION RULES 10 3 2 VIBRATIONAL SELECTION RULES 10 3 3 ROTATIONAL SELECTION RULES 10 3 4 TRANSITION FREQUENCIES 10 3 5 ASTRONOMICAL SPECTRA 10 4 NON-1? ELECTRONIC STATES 10 5 MASER EMISSIONS SOLUTIONS TO MODEL PROBLEMS FURTHER READING AND BIBLIOGRAPHY