Vibrational Spectroscopy of Molecular Liquids and Solids

460 Pages·1980·27.379 MB·English

by  A. D. Buckingham (auth.), S. Bratos, R. M. Pick (eds.)

Vibrational Spectroscopy
of Molecular Liquids
and Solids
NATO ADVANCED STUDY INSTITUTES SERIES
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Vibrational Spectroscopy
of Molecular Liquids
and Solids
Edited by
S. Bratos
and
R. M. Pick
Universite Pierre et Marie Curie
Paris, France
PLENUM PRESS • NEW YORK AND LONDON
Published in cooperation with NATO Scientific Affairs Division
Library of Congress Cataloging in Publication Data
NATO Advanced Study Institute on Vibrational Spectroscopy of Molecular Liquids and
Solids, Menton, 1979.
Vibrational spectroscopy of molecular liquids and solids.
(NATO advanced study institutes series: Series B, Physics; v. 56)
"Lectures presented at the NATO Advanced Study Institute on Vibrational Spectro
scopy of Molecular Liquids and Solids, held in Menton, France, June 25-July 7, 1979."
Includes indexes.
1. Vibrational spectra-Congresses. I. Bratos, S. II. Pick, R. M. III. Title. IV. Series.
QD96.V53N37 1979 539'.6 80-12174
ISBN-13: 978-1-4613-3113-1 e-ISBN-13: 978-1-4613-3111-7
DOl: 10.1007/978-1-4613-3111-7
Lectures presented at the NATO Advanced Study Institute on Vibrational Spectroscopy
of Molecular Liquids and Solids, held in Menton, France, June 25 -July 7, 1979.
© 1980 Plenum Press, New York
Softcover reprint of the hardcover 1s t edition 1980
A Division of Plenum Publishing Corporation
227 West 17th Street,New York,N.Y.10011
All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted,
in any form or by any means, electronic, mechanical, photocopying, microfIlming,
recording, or otherwise, without written permission from the publisher
'PREFACE
This book has its or1g1n in a NATO Summer School organized from
June 25 to July 7 1979, in Menton, France. The purpose of this
School was a comparative study of the various aspects of vibra
tional spectroscopy in molecular liquids and solids. This field has
been rapidly expanding in the last decade; unfortunately, its
development took place independently for liquids and for solids.
In these circumstances, the comparison of the basic concepts and
techniques used in these two branches of physics appeared as a
necessity. The lectures given at the Menton Advanced Study Institute,
as well as the exceptionally fruitful and lively discussions which
followed them confirmed this point of view.
The need of putting together these lectures, in the form of a
monograph, clearly appeared during the ASI and the lecturers accepted
to write down the material they presented at the Institute, improved
thanks to the remarks of the participants. It is the result of this
collective work which appears in the familiar Plenum Series.
The Editors would like to thank the Scientific Affairs Division
of NATO for the financial support it offered to the Institute, and
Dr. M. di Lullo, its director, for its constant help before and
during the School. They are also very happy to acknowledge the very
useful support of the Direction des Relations Universitaires Inter
nationales du Ministere des Universites, as well as the Conseil
Municipal of Menton who kindly accepted to have our Summer School
organized in his town. The Editors are grateful to all the authors
for their cooperation, as well as to Mrs. M. Debeau, E. Dervil,
J. Vincent and M. Yvinec for their scientific collaboration to this
project. Finally they would like to thank their constant collabor
ators, N. Claquin and C. Lanceron, who took a very important part
either in the preparation or in the every day life of the School and
in the publication of this book.
S. Bratos and R.M. Pick
CONTENTS
PART I INTRODUCTION
Intermolecular Forces 1
A.D. Buckingham
PART II LIQUIDS
Infrared and Raman Study of Vibrational
Relaxation in Liquids . . . • 43
S. Bratos
Rotational Spectral Band Shapes in Dense Fluids • • . • 61
W. A. Steele
Computer Calculation of Vibrational Band
Profiles in Liquids • . • 91
D. W. Oxtoby
Vibrational Relaxation of Hydrogen-bonded
Species in Solution: Fine Structure
of the v s (XH) Band . . . • . . • • • . • . . 101
G. N. Robertson
Experimental Study of Rotational and Vibrational
Relaxation in Liquids from Investigation
of the IR and Raman Vibrational Profiles 117
J. Vincent-Geisse
Collision-Induced Vibrational Spectroscopy
in Liquids 147
G. Birnbaum
Picosecond Vibrational Spectroscopy • • • • • • • • • . 167
A. Laubereau
vii
viii CONTENTS
Vibrational Bandshapes in Viscous Liquids
and Glasses . • • • • • . . • • 187
C. A. Angell
The Study of Vibrational Relaxation by
Ultrasonic and Light Scattering
Techniques 203
D. Sette
PART III SOLIDS
The Dynamics of Molecular Crystals: I.
General Theory . . . . • • • 221
S. Califano
The Dynamics of Molecular Crystals: II.
Intermolecular Potentials 231
S. Califano
The Dynamics of Molecular Crystals: III.
Infrared and Raman Intensity of
Lattice Bands • . . • . • . . • 243
S. Califano
The Dynamics of Molecular Crystals: IV.
Hamiltonian Perturbation Treatment 253
S. Califano
Large Amplitude Motions in Molecular Crystals 263
K. H. Michel
Raman and Infrared Lineshapes of Internal
Modes in ODIC Phases . • • . • • 305
R. M. Pick
Vibrational Band Shapes of Amorphous Solids 341
M. F. Thorpe
Order-Disorder Phase Transitions in Solids • • • . • . • 367
C. H. Perry
The Effect of Multiphonon Processes on
Vibrational Band Shapes in Molecular
Solids • . . • • • • . • • • . • • • 405
V. Schettino
CONTENTS ix
Neutron Spectroscopy Studies on Rotational
States in Molecular Solids • • • 415
H. Stiller
Rotation-translation Coupling in Collective
Modes of Molecular Solids and Liquids 431
G. Jaccuci
Participants 443
Author Index 451
Subj ect Index 459
Substance Index 463
INTERMOLECULAR FORCES
A.D. Buckingham
University Chemical Laboratory
Lensfield Road
Cambridge, CB2 lEW, United Kingdom
LECTURE 1
GENERAL SURVEY
1.1 Introduction
Molecules attract one another when they are far
apart, since liquids and solids exist. They repel one
another when close, since the densities of liquids and
solids have the values they do under normal conditions
of temperature and pressure. Figure 1.1 illustrates this
important truth and shows a typical interaction energy
u(R) of two spherical molecules as a function of their
separation R. For two argon atoms, the well-depth E is
0.198 x 10-20 J (Elk = 143 K) and the equilibrium separa
tion Re is 3.76 x 10-10 m (1,2).
Since we shall be concerned with intermolecular
forces, we should first consider what we mean by a molecule
and by a force (3). Two argon atoms form a bound diatomic
Ar2 but we do not normally consider the species Ar2 as a
molecule, since the binding energy is only about one-half
kT at room temperature. Collisions may easily dissociate
Ar2' and there are many thermally populated vibration
rotatio~ states, ~vJ' each with a different mean bond
length R ~ <~vJIRI~vJ>I<~VJi~vJ> and a large uncertainty
[<~vJI (R-R~I~vJ>I<~vJI~VJ>J 2 in R. We prefer to speak of
Ar2 as a dimer of argon atoms. Similarly H4' formed on
cooling gaseous hydrogen to about 20 K at 1 atmosphere,
is an infrared-active species in which two bonds are very
2 A. D. BUCKINGHAM
u(R)
~----~~------~~----~R
Figure 1.1. The interaction energy u (R} of two spher,tcal
molecules as a function of their separation R. The
distance ~ is known as the collision diameter,
similar to that in H2 (4); we prefer to think of H4 as
(H2)2, i.e. as the hydrogen molecule dimer. So by a
molecule we mean a group of atoms (or a single atom)
whose binding energy is large compared to kT, A molecule
therefore interacts with its environment wi.thout losing
its identity. In some non-rigid molecules, such as NH3'
1,2-dichloroethane (CICH2-CH2Cl), or a polypeptide, there
may be only a small change in energy with a large change
in an internal coordinate; the influence of the environ
ment in producing changes in the energy surface involving
this coordinate may be of interest (5).
And what do we mean by a force? In Figure 1.1 the
force is -du/dR and there is no difficulty here. The con
cept may easily be extended to a many-dimensional surface,
as in Figure 1.2 where the torque acting on a diatomic
molecule in collision with an atom is -aulae. But what
R
Figure 1.2. The three coordinates R, e, r appropriate to
the interaction of a diatomic molecule and a spherical
atom.