Wolfgang Demtroder. Laser Spectroscopy. Basic Concepts and Instrumentation. Second Enlarged Edition With 644 Figures and 91 Problems.

Transcription

1 Wolfgang Demtroder Laser Spectroscopy Basic Concepts and Instrumentation Second Enlarged Edition With 644 Figures and 91 Problems Springer

2 Contents 1. Introduction 1 2. Absorption and Emission of Light Cavity Modes Thermal Radiation and Planck's Law Absorption, Induced and Spontaneous Emission Basic Photometric Quantities Definitions Illumination of Extended Areas Discrete and Continuous Absorption and Emission Spectra Transition Probabilities Lifetimes. Spontaneous and Radiationless Transitions Semiclassical Description; Basic Equations Weak-Field Approximation Transition Probabilities with Broad-Band Excitation Phenomenological Inclusion of Decay Phenomena Interaction with Strong Fields Coherence Properties of Radiation Fields Temporal Coherence Spatial Coherence Coherence Volume The Coherence Function and the Degree of Coherence Coherence of Atomic Systems Density Matrix Coherent Excitation Relaxation of Coherently Excited Systems 53 Problems Widths and Profiles of Spectral Lines Natural Linewidth Lorentzian Line Profile of the Emitted Radiation Relation Between Linewidth and Lifetime Natural Linewidth of Absorbing Transitions Doppler Width Collision Broadening of Spectral Lines Phenomenological Description Theoretical Treatment of Elastic Collisions Relations Between Interaction Potential, Line Broadening and Shifts 80 IX

3 3.3.4 Collisional Narrowing of Lines Transit-Time Broadening Homogeneous and Inhomogeneous Line Broadening Saturation and Power Broadening Saturation of Level Population by Optical Pumping Saturation Broadening of Homogeneous Line Profiles Power Broadening Spectral Line Profiles in Liquids and Solids 95 Problems Spectroscopic Instrumentation Spectrographs and Monochromators Basic Properties 102 a) Speed of a Spectrometer 102 b) Spectral Transmission 104 c) Spectral Resolving Power 105 d) Free Spectral Range Ill Prism Spectrometer Ill Grating Spectrometer Interferometers Basic Concepts Michelson Interferometer Mach-Zehnder Interferometer Multiple-Beam Interference Plane Fabry-Perot Interferometer 140 a) The Plane FPI as a Transmission Filter 140 b) Illumination with Divergent Light 142 c) The Air-Spaced FPI Confocal Fabry-Perot Interferometer Multilayer Dielectric Coatings Interference Filters Birefringent Interferometer Tunable Interferometers Comparison Between Spectrometers and Interferometers Spectral Resolving Power Light-Gathering Power Accurate Wavelength Measurements Precision and Accuracy of Wavelength Measurements Today's Wavemeters 172 a) The Michelson-Wavemeter 172 b) Sigmameter 175 c) Computer-Controlled Fabry-Perot Wavemeter d) Fizeau Wavemeter Detection of Light Thermal Detectors Photodiodes 190

4 a) Photoconductive Diodes 192 b) Photovoltaic Detectors 193 c) Fast Photodiodes 195 d) Avalanche Diodes Photodiode Arrays Photoemissive Detectors 202 a) Photocathodes 202 b) Photocells 204 c) Photomultipliers 205 d) Photoelectric Image Intensifiers Detection Techniques and Electronic Equipment 212 a) Photon Counting 212 b) Measurements of Fast Transient Events 214 c) Optical Oscilloscope Conclusions 218 Problems Lasers as Spectroscopic Light Sources Fundamentals of Lasers Basic Elements of a Laser Threshold Condition Rate Equations Laser Resonators Open Optical Resonators Spatial Field Distributions in Open Resonators Confocal Resonators General Spherical Resonators Diffraction Losses of Open Resonators Stable and Unstable Resonators Ring Resonators Frequency Spectrum of Passive Resonators Spectral Characteristics of Laser Emission Active Resonators and Laser Modes Gain Saturation Spatial Hole Burning Multimode Lasers and Gain Competition Mode Pulling Experimental Realization of Single-Mode Lasers Line Selection Suppression of Transverse Modes Selection of Single Longitudinal Modes Intensity Stabilization Wavelength Stabilization Controlled Wavelength Tuning of Single-Mode Lasers Continuous Tuning Techniques Wavelength Calibration Linewidths of Single-Mode Lasers Tunable Lasers 297 XI

5 5.7.1 Basic Concepts Semiconductor-Diode Lasers Spin-Flip Raman Lasers Tunable Solid-State Lasers Color-Center Lasers Dye Lasers 312 a) Flashlamp-Pumped Dye Lasers 316 b) Pulsed-Laser-Pumped Dye Lasers 318 c) Continuous-Wave Dye Lasers Excimer Lasers Free-Electron Lasers Nonlinear Optical-Mixing Techniques Physical Background Second-Harmonic Generation Sum-Frequency and Higher-Harmonic Generation X-Ray Lasers Difference-Frequency Spectrometer Optical Parametric Oscillator Tunable Raman Lasers Gaussian Beams 358 Problems Doppler-Limited Absorption and Fluorescence Spectroscopy with Lasers Advantages of Lasers in Spectroscopy High-Sensitivity Methods of Absorption Spectroscopy Frequency Modulation Intracavity Absorption Direct Determination of Absorbed Photons Fluorescence Excitation Spectroscopy Photoacoustic Spectroscopy Optothermal Spectroscopy lonization Spectroscopy Basic Techniques 397 a) Photoionization 397 b) Collision-Induced lonization 397 c) Field lonization Sensitivity of lonization Spectroscopy Pulsed vs CW Lasers for Photoionization Resonant Two-Photon lonization Combined with Mass Spectrometry Thermionic Diode Optogalvanic Spectroscopy Velocity-Modulation Spectroscopy Laser Magnetic Resonance and Stark Spectroscopy Laser Magnetic Resonance Stark Spectroscopy Laser-Induced Fluorescence 414 XII

6 6.8.1 Molecular Spectroscopy by Laser-Induced Fluorescence Experimental Aspects of LIF LIF of Polyatomic Molecules Determination of Population Distributions by LIF Comparison Between the Different Methods 424 Problems Nonlinear Spectroscopy Linear and Nonlinear Absorption Saturation of Inhomogeneous Line Profiles Hole Burning Lamb Dips Saturation Spectroscopy Experimental Schemes Cross-Over Signals Intracavity Saturation Spectroscopy Lamb-Dip Frequency Stabilization of Lasers Polarization Spectroscopy Basic Principle Line Profiles of Polarization Signals Magnitude of Polarization Signals Sensitivity of Polarization Spectroscopy Advantages of Polarization Spectroscopy Multiphoton Spectroscopy Two-Photon Absorption Doppler-Free Multiphoton Spectroscopy Influence of Focussing on the Magnitude of the Two-Photon Signal Examples of Doppler-Free Two-Photon Spectroscopy Multiphoton Spectroscopy Special Techniques of Nonlinear Spectroscopy Saturated Interference Spectroscopy Doppler-Free Laser-Induced Dichroism and Birefringence Heterodyne Polarization Spectroscopy Combination of Different Nonlinear Techniques Conclusion 486 Problems Laser Raman Spectroscopy Basic Considerations Experimental Techniques of Linear Laser Raman Spectroscopy Nonlinear Raman Spectroscopy Stimulated Raman Scattering Coherent Anti-Stokes Raman Spectroscopy Resonant CARS and BOX CARS Hyper-Raman Effect 510 XIII

7 8.3.5 Summary of Nonlinear Raman Spectroscopy Applications of Laser Raman Spectroscopy 512 Problems Laser Spectroscopy in Molecular Beams Reduction of Doppler Width Adiabatic Cooling in Supersonic Beams Formation and Spectroscopy of Clusters and Van der Waals Molecules in Cold Molecular Beams Nonlinear Spectroscopy in Molecular Beams Laser Spectroscopy in Fast Ion Beams Applications of FIBLAS Spectroscopy of Radioactive Elements Photofragmentation Spectroscopy of Molecular Ions Laser Photodetachment Spectroscopy Saturation Spectroscopy in Fast Beams Spectroscopy in Cold Ion Beams Combination of Molecular Beam Laser Spectroscopy and Mass Spectrometry 548 Problems Optical Pumping and Double-Resonance Techniques Optical Pumping Optical-RF Double-Resonance Technique Basic Considerations Laser RF Double-Resonance Spectroscopy in Molecular Beams Optical-Microwave Double Resonance Optical-Optical Double Resonance Simplification of Complex Absorption Spectra Step wise Excitation and Spectroscopy of Rydberg States Stimulated-Emission Pumping Special Detection Schemes of Double-Resonance Spectroscopy OODR-Polarization Spectroscopy Polarization Labelling Microwave-Optical Double-Resonance Polarization Spectroscopy Hole-Burning and Ion-Dip Double-Resonance Spectroscopy Triple-Resonance Spectroscopy 590 Problems Time-Resolved Laser Spectroscopy Generation of Short Laser Pulses Time Profiles of Pulsed Lasers Q-Switched Lasers 597 XIV

8 Cavity Dumping Mode-Locking of Lasers 601 a) Active Mode-Locking 602 b) Passive Mode-Locking 606 c) Synchroneous Pumping with Mode-Locked Lasers Generation of Femtosecond Pulses 610 a) The Colliding Pulse Mode-Locked Laser 610 b) Lower Limit of Pulse Width Optical Pulse Compression Solition Laser Generation of High-Power Ultrashort Pulses Measurement of Ultrashort Pulses Streak Camera Optical Correlator for Measuring Ultrashort Pulses Lifetime Measurements with Lasers Phase-Shift Method Single-Pulse Excitation Delayed-Coincidence Technique Lifetime Measurements in Fast Beams Pump and Probe Technique Pump-and-Probe Spectroscopy of Collisional Relaxation in Liquids Electronic Relaxation in Semiconductors Femtosecond Transition State Dynamics Real-Time Observations of Molecular Vibrations Problems 647 Coherent Spectroscopy Level-Crossing Spectroscopy Classical Model for the Hanle Effect Quantum-Mechanical Models Experimental Arrangements Examples Stimulated Level-Crossing Spectroscopy Quantum-Beat Spectroscopy Basic Principles Experimental Techniques Molecular Quantum-Beat Spectroscopy Optical Pulse-Train Interference Spectroscopy Photon Echoes Optical Nutation and Free Induction Decay Heterodyne Spectroscopy Correlation Spectroscopy Basic Considerations Homodyne Spectroscopy Heterodyne Correlation Spectroscopy 690 Problems 693 xv

9 13. Laser Spectroscopy of Collision Processes High-Resolution Laser Spectroscopy of Collisional Line Broadening and Line Shifts Sub-Doppler Spectroscopy of Collision Processes Combination of Different Techniques Measurements of Inelastic Collision Cross Sections of Excited Atoms and Molecules Measurements of Absolute Quenching Cross Sections Collision-Induced Rovibronic Transitions in Excited States Collisional Transfer of Electronic Energy Energy Pooling in Collisions Between Excited Atoms Spectroscopy of Spin-Flip Transitions Spectroscopic Techniques for Measuring Collision-Induced Transitions in the Electronic Ground State of Molecules Time-Resolved Infrared Fluorescence Detection Time-Resolved Absorption and Double-Resonance Methods Collision Spectroscopy with CW Lasers Collisions Involving Molecules in High Vibrational States Spectroscopy of Reactive Collisions Spectroscopic Determination of Differential Collision Cross Sections in Crossed Molecular Beams Photon-Assisted Collisional Energy Transfer 731 Problems New Developments in Laser Spectroscopy Optical Cooling and Trapping of Atoms Photon Recoil Measurements of the Recoil Shift Optical Cooling by Photon Recoil Experimental Arrangements Induced Dipole Forces in a Radiation Field Optical Trapping of Atoms Cooling Limits Applications of Cooled Atoms Spectroscopy of Single Ions Trapping of Ions Optical Sideband Cooling Direct Observations of Quantum Jumps Formation of Wigner Crystals in Ion Traps Laser Spectroscopy in Storage Rings Optical Ramsey Fringes Basic Considerations Two-Photon Ramsey Resonances Nonlinear Ramsey Fringes Using Three Separated Fields 775 XVI

10 Observation of Recoil Doublets and Suppression of One Recoil Component Atom Interferometry The One-Atom Maser Spectral Resolution Within the Natural Linewidth Time-Gated Coherent Spectroscopy Coherence and Transit Narrowing Raman Spectroscopy with Sub-Natural Linewidth Absolute Optical-Frequency Measurement and Optical-Frequency Standards Squeezing Amplitude and Phase Fluctuations of a Light Wave Experimental Realization of Squeezing Application of Squeezing to Gravitational Wave Detectors Applications of Laser Spectroscopy Applications in Chemistry Laser Spectroscopy in Analytical Chemistry Laser-Induced Chemical Reactions Laser Femtosecond-Chemistry Isotope Separation with Lasers Summary of Laser Chemistry Environmental Research with Lasers Absorption Measurements Atmospheric Measurements with LIDAR Spectroscopic Detection of Water Pollution Applications to Technical Problems Spectroscopy of Combustion Processes Applications of Laser Spectroscopy to Materials Science Measurements of Flow Velocities in Gases and Liquids Applications in Biology Energy Transfer in DNA Complexes Time-Resolved Measurements of Biological Processes Correlation Spectroscopy of Microbe Movements Laser Microscope Medical Applications of Laser Spectroscopy Applications of Raman Spectroscopy in Medicine Heterodyne Measurements of Ear Drums Cancer Diagnostics and Therapy with the HPD Technique Laser Lithotripsy Concluding Remarks 841 References 843 Subject Index 917 XVII