Torre Time-Resolved Spectroscopy in Complex Liquids

An Experimental Perspective
1. Auflage 2007
ISBN: 978-0-387-25558-3
Verlag: Springer-Verlag
Format: PDF
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 252 Seiten

The investigation of liquid properties is as old as the human desire to observe natural phenomena. The paramount relevance of such state of matter is - vious, spanning from the basic theoretical model of random systems to the more advanced technical applications. Nevertheless the interpretation and - derstanding of liquid properties remains a challenge in materials science. In the liquid state, the potential and kinetic energies are characterized by similarvalues,differentlyfromthegasorsolid/crystalphases.Thisfundamental physical property prevents a description of the liquid structure independently fromitsdynamics.Theintermolecularforcesandmolecularmotionsarestrictly interconnected, producing the peculiar features of liquid phases. In particular when the intermolecular potential is characterized by speci?c features,asanisotropicand/orlong-rangeinteractions,theliquidstateshows- cal dynamic aggregation and structuring phenomena. This is the distinguishing characteristic of complex liquids. Typical examples are the hydrogen-bonded liquids, glass formers, polymers and liquid crystals. Also relatively simple molecular liquids, e.g., CS and benzene, clearly show complex dynamics, 2 evidence of local structuring effects. During the last years, researchers have undertaken a steady effort to improve the knowledge of liquid matter, both from experimental and theoretical points of view. New spectroscopic techniques, based on nonlinear optical phenomena, have been realized and applied to the study of simple molecular liquids. On the other hand, standard experiments have been applied to liquids characterized by particularly complex dynamic processes.

Autoren/Hrsg.

Torre, Renato

Inhaltsverzeichnis

1;Contents;6
2;Contributing Authors;8
3;Preface;10
4;Chapter 1 TWO DIMENSIONAL FIFTH-ORDER RAMAN SPECTROSCOPY A New Tool for the Study of Liquid State Dynamics;12
4.1;1.1 Introduction;13
4.2;1.2 Theory;21
4.2.1;1.2.1 Origin of the Fifth-Order Raman Signal;24
4.2.2;1.2.2 Theoretical Results Summary;25
4.3;1.3 Experimental Advances;37
4.3.1;1.3.1 Laser Source and Experiment Synopsis;40
4.3.2;1.3.2 Diffractive Optics;42
4.3.3;1.3.3 Heterodyne Detection;45
4.3.4;1.3.4 Multicolor Approach;46
4.3.5;1.3.5 Cascaded Signals;46
4.4;1.4 Experimental Findings;51
4.5;1.5 General Discussion and Implications of the Findings for the Liquid State;65
4.6;1.6 Summary and Future Perspective;71
4.7;Acknowledgments;74
4.8;References;75
5;Chapter 2 OPTICAL KERR EFFECT EXPERIMENTS ON COMPLEX LIQUIDS A Direct Access to Fast Dynamic Processes;84
5.1;2.1 Introduction;84
5.2;2.2 Time-Resolved OKE Experiments;85
5.2.1;2.2.1 A Simple Model;87
5.2.2;2.2.2 The Nonlinear Optics Framework;90
5.3;2.3 The Response Function;93
5.3.1;2.3.1 The Linear Susceptibility Tensor and Its Correlation;95
5.3.2;2.3.2 The Model of Liquid Dynamics;99
5.4;2.4 The Experimental Procedure;105
5.4.1;2.4.1 Heterodyne Detection;110
5.4.2;2.4.2 HD-OKE vs. Light Scattering Signal;114
5.5;2.5 Some Experimental Results;115
5.5.1;2.5.1 HD-OKE in "Simple" Molecular Liquids;115
5.5.2;2.5.2 HD-OKE in Supercooled Liquids and Glass- Formers;122
5.5.3;2.5.3 The Water Case;125
5.6;Acknowledgments;128
5.7;Appendix: Laser Pulses Definition;128
5.8;Notes;130
5.9;References;130
6;Chapter 3 TRANSIENT GRATING EXPERIMENTS IN GLASS- FORMER LIQUIDS A Unique Tool to Investigate Complex Dynamics;139
6.1;3.1 Introduction;139
6.2;3.2 Theory of the Transient Grating Experiment;141
6.2.1;3.2.1 TG and Four-Wave Mixing;144
6.2.2;3.2.2 Hydrodynamic Approach to the TG Experiments;151
6.3;3.3 Experimental Procedure;161
6.3.1;3.3.1 Laser System and Optical Setup;161
6.3.2;3.3.2 Heterodyne and Homodyne Detections;164
6.3.3;3.3.3 Fitting Procedure;166
6.4;3.4 Experimental Results;167
6.4.1;3.4.1 SupercooledWater: the Importance of the Photothermal Effect;171
6.4.2;3.4.2 Ortho-terphenyl: the Structural Dynamics of a Fragile Glass-Former;175
6.4.3;3.4.3 Glycerol: A Test of Hydrodynamic Models;180
6.4.4;3.4.4 Meta-Toluidine: The Rotation-Translation Coupling Effect;184
6.5;Acknowledgments;188
6.6;Appendix: Mathematical Representation of the Stretched Exponential;188
6.7;Notes;189
6.8;References;190
7;Chapter 4 DYNAMICAL PROCESSES IN CONFINED LIQUID CRYSTALS;195
7.1;4.1 Introduction;195
7.2;4.2 Continuum Description of Nematic Liquid Crystals;197
7.3;4.3 Fluctuational Dynamics in Nematic Liquid Crystals;199
7.4;4.4 Light Scattering by Director Fluctuations;200
7.5;4.5 Confined Liquid Crystals;202
7.5.1;4.5.1 Planar Cells;202
7.5.2;4.5.2 Polymer Dispersed Liquid Crystals;203
7.5.3;4.5.3 Holographic Polymer Dispersed Liquid Crystals;203
7.6;4.6 Fluctuation Spectrum in Confined Geometries;204
7.6.1;4.6.1 Fluctuation Dynamics in Thin Planar Cells;205
7.6.2;4.6.2 Relaxation Dynamics in PDLCs;209
7.6.3;4.6.3 Relaxation Dynamics in HPDLCs;209
7.7;4.7 Dynamic Light Scattering Experiments;210
7.7.1;4.7.1 Planar Samples;211
7.7.2;4.7.2 HPDLCs;216
7.8;4.8 Conclusions;222
7.9;References;223
8;Chapter 5 TIME- RESOLVED FLUORESCENCE AND DICHROISM IN ABSORBING LIQUIDS Intermolecular Guest- Host Interactions in Absorbing Liquids;227
8.1;5.1 Introduction;227
8.2;5.2 Photoinduced Molecular Reorientation of Absorbing Liquids and Liquid Crystals;229
8.3;5.3 Theory;233
8.3.1;5.3.1 TRPS fluorescence;234
8.3.2;5.3.2 TRPS Pump-Probe Dichroism;236
8.4;5.4 Fluorescence Experiments: Observing the Molecule Rotation in its Excited State;238
8.4.1;5.4.1 Deuterium Effect on Molecular Rotation and its Relationship with Optical Nonlinearity;240
8.4.2;5.4.2 Effect of Excitation-LightWavelength on Dye Excitation and its Relationship with Optical Nonlinearity;243
8.5;5.5 Combining Fluorescence and Dichroism Experiments: The Influence of Electronic Excitation on Rotational Friction;246
8.6;5.6 Conclusions: The Role of Hydrogen Bonding;249
8.7;References;251
9;Topic Index;256