Time-Resolved Spectroscopy in Complex Liquids An Experimental Perspective

Transcription

1 Time-Resolved Spectroscopy in Complex Liquids An Experimental Perspective

2 Renato Torre Editor Time-Resolved Spectroscopy in Complex Liquids An Experimental Perspective ABC

3 Renato Torre European Lab for Non-linear Spectroscopy (LENS) and Dip. di Fisica, Polo Scientifico, University of Firenze, Via Nello Carrara 1, I Sesto Fiorentino, Firenze, Italy Time-Resolved Spectroscopy in Complex Liquids Consulting Editor: D. R. Vij Kurukshetra University E-5 University Campus Kurukshetra India Library of Congress Control Number: ISBN e-isbn Printed on acid-free paper Springer Science+Business Media, LLC All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper springer.com

4 Nel mezzo del cammin di nostra vita mi ritrovai per una selva oscura, ché la diritta via era smarrita. In the middle of my life s jorney I woke to find myself in a dark wood, where the right road was wholly lost and gone. Dante Alighieri (Firenze, 1265)

5 Contents Contributing Authors ix Preface 1 Two Dimensional Fifth-Order Raman Spectroscopy 1 Christopher J. Milne, Yun-Liang Li, and R. J. Dwayne Miller 1.1 Introduction Theory Experimental Advances Experimental Findings General Discussion and Implications of the Findings for the Liquid State Summary and Future Perspective 60 2 Optical Kerr Effect Experiments on Complex Liquids 73 Paolo Bartolini, Andrea Taschin, Roberto Eramo, and Renato Torre 2.1 Introduction Time-Resolved OKE Experiments The Response Function The Experimental Procedure Some Experimental Results 104 Appendix: Laser Pulses Definition Transient Grating Experiments in Glass-Former Liquids 129 Andrea Taschin, Roberto Eramo, Paolo Bartolini, and Renato Torre 3.1 Introduction Theory of the Transient Grating Experiment Experimental Procedure Experimental Results 157 Appendix: Mathematical Representation of the Stretched Exponential 178 xi

6 viii TIME-RESOLVED SPECTROSCOPY IN COMPLEX LIQUIDS 4 Dynamical Processes in Confined Liquid Crystals 185 M. Vilfan, I. Drevenšek Olenik, and M. Čopič 4.1 Introduction Continuum Description of Nematic Liquid Crystals Fluctuational Dynamics in Nematic Liquid Crystals Light Scattering by Director Fluctuations Confined Liquid Crystals Fluctuation Spectrum in Confined Geometries Dynamic Light Scattering Experiments Conclusions Time-Resolved Fluorescence and Dichroism in Absorbing Liquids 217 D. Paparo, C. Manzo, and L. Marrucci 5.1 Introduction Photoinduced Molecular Reorientation of Absorbing Liquids and Liquid Crystals Theory Fluorescence Experiments: Observing the Molecule Rotation in its Excited State Combining Fluorescence and Dichroism Experiments: The Influence of Electronic Excitation on Rotational Friction Conclusions: The Role of Hydrogen Bonding 239 Topic Index 247

7 Contributing Authors Bartolini, Paolo European Lab. for Non-Linear Spectroscopy (LENS), Universitá di Firenze, via N. Carrara 1, I Sesto Fiorentino, Firenze, Italy INFM-CRS-SOFT c/o Univ. la Sapienza, Roma, Italy Čopič, Martin Faculty of Mathematics and Physics, University of Ljubljana, Slovenia J. Stefan Institute, Jamova 39, Ljubljana, Slovenia Drevenšek Olenik, Irena Faculty of Mathematics and Physics, University of Ljubljana, Slovenia J. Stefan Institute, Jamova 39, Ljubljana, Slovenia Eramo, Roberto European Lab. for Non-Linear Spectroscopy (LENS), Universitá di Firenze, via N. Carrara 1, I Sesto Fiorentino, Firenze, Italy INFM-CRS-SOFT c/o Univ. la Sapienza, Roma, Italy Li, Yun-Liang Departments of Chemistry and Physics, Institute of Optical Sciences, University of Toronto, 60 St. George St., Toronto, Ontario, Canada Manzo, Carlo CNR-INFMCoherentia, Universitá Federico II c/o Dip. Scienze Fisiche, Complesso Univ. Monte S. Angelo, via Cintia, I Napoli, Italy

8 x TIME-RESOLVED SPECTROSCOPY IN COMPLEX LIQUIDS Marucci, Lorenzo CNR-INFMCoherentia, Universitá Federico II c/o Dip. Scienze Fisiche, Complesso Univ. Monte S. Angelo, via Cintia, I Napoli, Italy Miller, R. J. Dwayne Departments of Chemistry and Physics, Institute of Optical Sciences, University of Toronto, 60 St. George St., Toronto, Ontario, Canada Milne, Christopher J. Department of Chemistry, University of Toronto, Canada Present Address: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen, Switzerland Paparo, Domenico CNR-INFMCoherentia, Universitá Federico II c/o Dip. Scienze Fisiche, Complesso Univ. Monte S. Angelo, via Cintia, I Napoli, Italy Taschin, Andrea European Lab. for Non-Linear Spectroscopy (LENS), Universitá di Firenze, via N. Carrara 1, I Sesto Fiorentino, Firenze, Italy INFM-CRS-SOFT c/o Univ. la Sapienza, Roma, Italy Torre, Renato European Lab. for Non-Linear Spectroscopy (LENS) and Dip. di Fisica, Universitá di Firenze, via N. Carrara 1, I Sesto Fiorentino, Firenze, Italy INFM-CRS-SOFT c/o Univ. la Sapienza, Roma, Italy Vilfan, Mojca J. Stefan Institute Jamova 39, Ljubljana, Slovenia

9 Preface 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 obvious, spanning from the basic theoretical model of random systems to the more advanced technical applications. Nevertheless the interpretation and understanding of liquid properties remains a challenge in materials science. In the liquid state, the potential and kinetic energies are characterized by similar values, differently from the gas or solid/crystal phases. This fundamental physical property prevents a description of the liquid structure independently from its dynamics. The intermolecular forces and molecular motions are strictly interconnected, producing the peculiar features of liquid phases. In particular when the intermolecular potential is characterized by specific features, as anisotropic and/or long-range interactions, the liquid state shows local 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 2 and benzene, clearly show complex dynamics, 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. In this book, we collect a series of chapters dedicated to the state-of-art studies of optical spectroscopy in the time domain on complex liquids of different nature. In Chap. 1, a new nonlinear spectroscopic technique, 2D-Raman, is comprehensively reviewed. This is probably the most promising experimental tool able to collect truly new information on fast dynamics in liquid matter. Chapter 2 is dedicated to optical Kerr effect techniques and to the investigation of relaxation dynamics in complex liquids, inclusive of relative slow collective

10 xii TIME-RESOLVED SPECTROSCOPY IN COMPLEX LIQUIDS phenomena. Transient grating spectroscopy is reviewed in Chap. 3, introducing the recent experimental improvements and their application to the study of viscoelastic phenomena in glass formers. Chapter 4 describes the dynamics of confined liquid crystals as measured by dynamic light scattering experiments. In Chap. 5, the host guest interactions of dye molecules in liquid-crystal matter is analyzed by time-resolved fluorescence and dichroism spectroscopy. Firenze RENATO TORRE