Laboratory Astrochemistry: From Molecules through Nanoparticles to Grains

Laboratory Astrochemistry
Contents
List of Contributors
Preface
Chapter 1 The Astrophysical Background
1.1 The Contents of this Volume
References
Chapter 2 Molecular Spectroscopy
2.1 Electronic Spectroscopy of Potential Carriers of Diffuse Interstellar Bands
2.1.1 Introduction
2.1.2 Laboratory Methods
2.1.2.1 Resonant Two-Color Two-Photon Ionization
2.1.2.2 Resonant Two-Color Photodetachment
2.1.2.3 Resonant Two-Color, Two-Photon Fragmentation
2.1.2.4 Cavity Ringdown Spectroscopy
2.1.2.5 Four-Wave Mixing Technique
2.1.2.6 Laser-Induced Fluorescence
2.1.3 Species of Astrophysical Interest
2.1.3.1 Molecular Ions
2.1.3.2 Bare Carbon Chains
2.1.3.3 Metal-Containing Carbon Chains
2.1.4 Outlook
Acknowledgments
2.2 UV--Vis Gas-Phase Absorption Spectroscopy of PAHs
2.2.1 Introduction
2.2.2 Experimental
2.2.2.1 Supersonic Jet Cavity Ringdown Spectrometer
2.2.2.2 Matrix-Isolation Spectroscopy
2.2.3 Data Analysis
2.2.3.1 Derivation of Absorption Cross Sections
2.2.3.2 Extrapolation of Gas-Phase Transitions from MIS Data
2.2.4 Results and Discussion
2.2.5 Conclusion
Acknowledgments
2.3 Laboratory IR Spectroscopy of PAHs
2.3.1 Introduction
2.3.2 Laboratory Spectroscopic Methods
2.3.2.1 Neutral PAHs
2.3.2.2 Cationic PAHs
2.3.2.3 Computational
2.3.2.4 Comparison of Experimental Methods
2.3.3 Far-Infrared Spectroscopy
2.3.3.1 Laboratory Results
2.3.4 IR Spectral Features of PAHs
2.3.5 PAH Derivatives and Related Species
2.3.5.1 Nitrogen-Substituted PAHs
2.3.5.2 Protonated PAHs
2.3.5.3 Hydrogenated and Dehydrogenated PAHs
2.3.5.4 Metal--PAH Complexes
2.3.5.5 Other PAH Modifications
2.3.6 Conclusions
2.4 The Spectroscopy of Complex Molecules
2.4.1 Introduction
2.4.2 General Spectroscopic Considerations
2.4.3 The Quest for Interstellar Glycine
2.4.4 General Astronomic Considerations
2.4.5 Alkyl Alcohols
2.4.5.1 Methanol, CH3OH
2.4.5.2 Ethanol, C2H5OH
2.4.5.3 Larger alkanols
2.4.5.4 Alkanediols and -polyols
2.4.6 Alkyl Ethers
2.4.6.1 Dimethyl, Ether CH3OCH3
2.4.6.2 Larger Ethers
2.4.7 Esters
2.4.8 Alkyl Cyanides
2.4.9 Other Complex Molecules
References
Chapter 3 Gas Phase Chemistry
3.1 Introduction
3.1.1 Cross Sections and Rate Coefficients for Binary Collisions
3.1.2 Differential Scattering and Crossed Beam Experiments
3.1.3 Low-Energy Collisions in Merged Beams and Integral Cross Sections
3.1.4 Low-Temperature Collisions in Beams and Traps, Thermal Rate Coefficients
3.1.4.1 Selected Ion Flow Tubes
3.1.4.2 Laval Nozzle Expansions
3.1.4.3 Trap Experiments
Acknowledgment
3.2 Dissociative Recombination
3.2.1 Principle and Main Occurrence
3.2.1.1 Mechanisms of Dissociative Recombination
3.2.1.2 Dissociative Recombination in Astronomical Environments
3.2.2 Methods of Laboratory Study
3.2.2.1 Multicollisional Swarm Methods
3.2.2.2 Single-Collision Beam Methods
3.2.3 Recent Laboratory Results and their Impact on Molecular Astrophysics
3.2.3.1 DR of the Triatomic Hydrogen Ion H3+
3.2.3.2 Branching Ratios and Internal Excitation for Molecular Fragments from DR
3.2.3.3 DR and Formation of Interstellar Methanol
3.2.3.4 DR of Protonated Nitriles in Titan's Ionosphere
3.3 Inelastic Processes
3.3.1 Introduction
3.3.2 Molecular Beam Measurements of Inelastic Scattering in Water
3.3.3 Laser Ionization of Molecular Hydrogen and Nascent Water
3.3.4 Experimental Details
3.3.4.1 Density to Flux Correction and Relative Collision Cross Sections
3.3.4.2 Temperature Control
3.3.5 Calculating Differential and Total Cross Sections
3.3.6 Water--Hydrogen Molecule PES
3.3.7 Dynamical Calculations
3.3.7.1 Total Cross Sections and Rates
3.3.7.2 Differential Cross Sections
3.3.8 Theory and Experiments Comparisons
3.3.8.1 Differential Cross Sections
3.3.8.2 Total Cross Sections
3.3.8.3 Other Scattering Experiments
3.4 Low Temperature Trapping Experiments
3.4.1 N+ + H2
3.4.2 H3+ + H2
3.4.3 Deuterium Fractionation
3.4.4 Trap Experiments on Deuterium Enrichment
3.4.5 Toward State-to-State Rate Coefficients
3.5 Negative Ion Chemistry in the Early Universe
3.5.1 Introduction: Negative Ions in Space
3.5.2 The Chemistry of the Early Universe
3.5.3 H2 Formation by Associative Detachment of H- and H
3.5.4 H- Photodetachment
3.5.5 Mutual Neutralization of H- and H+
3.5.6 Summary
Acknowledgments
References
Chapter 4 Molecular Photodissociation
4.1 Introduction
4.2 Photodissociation Processes
4.2.1 Small Molecules
4.2.2 Large Molecules
4.3 Photodissociation Cross Sections
4.3.1 Theory
4.3.1.1 Born--Oppenheimer approximation
4.3.1.2 Electronic Energies: Method of Configuration Interaction
4.3.1.3 Nuclear Dynamics: Oscillator Strengths and Cross Sections
4.3.2 Experiments
4.3.3 Photodissociation Products
4.4 Astrophysical Radiation Fields
4.4.1 General Interstellar Radiation Field
4.4.2 Stellar Radiation Fields
4.4.3 Lyman α Radiation
4.4.4 Cosmic-Ray-Induced Photons
4.4.5 Dust Attenuation
4.4.6 Self-Shielding
4.5 Photodissociation Rates
4.6 Photodissociation of CO and its Isotopologs
4.7 Photostability of PAHs
4.8 Summary
Acknowledgments
References
Chapter 5 Surface Science
5.1 Introduction
5.1.1 Surface Reactions under Interstellar Conditions
5.1.2 Experimental Methods
5.1.3 Introducing the Hot Topic Sections
5.1.4 Outlook
5.2 Molecular Hydrogen Formation on Carbonaceous Surfaces
5.2.1 Interaction of Atomic Hydrogen with Carbonaceous Surfaces
5.2.2 Formation of Molecular Hydrogen on Carbonaceous Surfaces
5.2.3 Energy Partitioning in H2 Formation
5.2.4 Summary and Outlook
5.3 The Influence of Ice Morphology on Interstellar Chemistry
5.3.1 The Structure of Amorphous Solid Water (ASW)
5.3.2 Desorption of Molecular Hydrogen
5.3.3 Influence of the Morphology of the Ice on the Sticking of Hydrogen
5.3.4 Recombination Process
5.3.5 Energetic Balance of the H2 Reaction and its Consequences on the Morphology of Ice
5.3.6 The Impact of Ice Morphology on Thermal Desorption Processes for Other Small Molecules
5.3.7 ASW Morphology Changes due to Ion and UV Irradiation
5.4 Solid-State Pathways toward Molecular Complexity in Space
5.4.1 General Information on Experimental Techniques
5.4.2 Atom Bombardment
5.4.2.1 Introduction
5.4.2.2 Experimental Setup
5.4.3 O/O2/O3 + H
5.4.4 UV Photoprocessing
5.4.4.1 Introduction
5.4.4.2 Radiation-Induced Dynamics and Chemistry in Ices
5.4.4.3 Experiment
5.4.4.4 UV Photodesorption Experiments and Key Results
5.4.4.5 Photochemistry Experiments
5.4.4.6 Other Ice Photochemistry Studies
Acknowledgments
5.5 New Calculational Strategies for Including Surface Reactions in Astrochemical Network Models
5.5.1 Rate Equations
5.5.2 Stochastic Methods
5.5.3 Modified Rate Equations
5.5.4 Microscopic Studies: A Kinetic Monte Carlo Approach
5.5.5 Summary
References
Chapter 6 Dust and Nanoparticle Spectroscopy
6.1 Introduction I: Spectroscopic Observations of Cosmic Dust
6.1.1 Dust in the Interstellar Medium
6.1.2 Stardust
6.1.3 Dust in Planetary and Protoplanetary Systems
6.2 Introduction II: Techniques in Laboratory Dust Spectroscopy
6.2.1 Calculated Versus Measured Comparison Spectra
6.2.2 Measuring Dust Absorption Spectra
6.2.3 Determination of Optical Constants of Solids
6.3 The Bulk of Interstellar Dust: Amorphous Silicates
6.3.1 Structure of Silicates
6.3.2 Production Techniques for Amorphous Silicates
6.3.3 The Infrared Spectra of Amorphous Silicates
6.3.4 Optical Constants at UV/Vis/NIR Wavelengths
6.3.5 The Far-Infrared Emissivity of Cold Amorphous Silicates
6.4 Crystalline Silicates
6.4.1 The Effect of Silicate Composition on Infrared Spectra
6.4.2 Temperature Effects on Infrared Spectra of Olivine and Pyroxene Particles
6.4.3 Optical Constants of Olivine at Room Temperature and Low Temperature
6.4.4 Structural Defects of Silicates
6.4.5 Shape Effects and Medium Effects on Infrared Spectra of Forsterite
6.4.6 The missing Iron Content Problem
6.5 Oxides as High-Temperature Condensates
6.5.1 The Role of Oxide Dust in the Cosmic Matter Circuit
6.5.2 A General Remark on the IR Bands of Refractory Oxides
6.5.3 Al Oxides, Ca--Al Oxides, and Mg--Al Oxides
6.5.4 Silicon Oxides (SiO2 and SiO)
6.5.5 Iron Oxides and Mg--Fe Oxides
6.5.6 Titanium Oxides
6.5.7 Constraining the Optical Constants in the NIR Region
6.5.8 Temperature Dependence of the Optical Constants
6.6 Spectroscopic Properties of Carbon Compounds
6.6.1 Graphite, Diamond, and Fullerite
6.6.2 Hydrogenated Amorphous Carbon
6.6.3 Silicon Carbide and Other Carbides
6.7 Photoluminescence Studies of Silicon-Based Nanoparticles
6.7.1 Effects of Nanoscale Particle Size
6.7.2 PL Spectra of Free Si NCs
6.7.3 PL Spectra of Matrix-Embedded Si NCs
6.7.4 PL Spectra of Silicon Dioxide NPs
6.7.5 Consequences for the Interpretation of PL Observations
Acknowledgments
References
Chapter 7 Formation of Nanoparticles and Solids
7.1 Condensation of Cosmic Dust in Astrophysical Environments
7.1.1 Element Abundances in Dust-Forming Objects
7.1.1.1 Cosmic Standard Mixture
7.1.2 AGB Stars
7.1.2.1 Element Abundance Evolution on the AGB
7.1.3 Massive Stars
7.1.4 Condensation Sequences
7.1.5 Principles of the Dust Formation Process
7.1.6 Condensation Temperature
7.1.7 Reaction Kinetics
7.1.8 Mineral Formation in M Stars
7.1.8.1 Gas-Phase Composition
7.1.8.2 Seed Particles
7.1.9 Condensation of Carbonaceous Grains in C Stars
7.1.9.1 Carbon Stars on the AGB
7.1.9.2 Other Carbon-Rich Stars
7.1.9.3 Predictions from Equilibrium Calculations
7.1.9.4 Molecular Composition of Outflowing Gas
7.1.9.5 Formation of PAHs in AGB Stars
7.1.10 Formation of Minerals in C Stars
7.1.11 Concluding Remarks
7.2 Laboratory Approach to Gas-Phase Condensation of Particles
7.2.1 Gas-Phase Condensation Methods in the Laboratory
7.2.2 Laboratory Tools for the Characterization of Condensation Products
7.3 Gas-phase Condensation Experiments of Magnesium Iron Silicates
7.3.1 Grain Production and Characterization
7.3.2 Grain Compositions
7.3.3 Magnesium Iron Silicates
7.3.4 Time Versus Temperature
7.4 Gas-Phase Condensation of Carbonaceous Particles in the Laboratory
7.4.1 Condensation Pathways of Carbon Nanograins at Different Temperatures
7.4.2 Characterization of the Condensation Products
7.4.3 Formation Pathways of Carbon Grains and Astrophysical Discussion
7.4.4 Spectral Properties of the HT and LT Condensates
7.5 Processing of Silicates
7.5.1 Thermal Annealing
7.5.2 Ion Bombardment
7.6 Carbon Dust Modifications under Thermal Annealing and Irradiation by UV Photons, Ions, and H Atoms
7.6.1 Thermal Annealing
7.6.2 UV Irradiation
7.6.3 Ion Bombardment
7.6.4 H-Atom Irradiation
7.6.5 Conclusions
Acknowledgments
References
Index
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