Advances in Multi-Photon Processes and Spectroscopy: (Volume 21)

257 Pages·2013·8.83 MB·English

by  A A Villaeys, Y Fujimura

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Volume
21
World Scientifc
NEW J E R S E Y • L O N D O N • S I N G A P O R E • B E I J I N G • S H A N G H A I • H O N G K O N G • TA I P E I • C H E N N A I
8851hc.9789814518338.tp.indd 2 28/10/13 10:16 AM
Published by
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Library of Congress Control Number: 86643116
Advances in Multi-Photon Processes and Spectroscopy — Vol. 21
ADVANCES IN MULTI-PHOTON PROCESSES AND SPECTROSCOPY
(Volume 21)
Copyright © 2014 by World Scientific Publishing Co. Pte. Ltd.
All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means,
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ISBN 978-981-4518-33-8
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PREFACE
In view of the rapid growth in both experimental and theoretical studies
of multi-photon processes and multi-photon spectroscopy of molecules,
it is desirable to publish an advanced series that contains review articles
readable not only by active researchers, but also by those who are not yet
experts and intend to enter the field. The present series attempts to serve this
purpose. Each chapter is written in a self-contained manner by experts in
the area so that readers can grasp the content without too much preparation.
This volume consists of six chapters. The first chapter presents the
results of both theoretical and experimental studies of “Vibrational and
Electronic Wavepackets Driven by Strong Field Multi-photon Ionization”.
First, basic theoretical ideas essential to understanding multiphoton ioniza-
tion and laser control of molecules are described. Secondly, experimental
techniques for molecular control such as phase-dependent dissociation,
photon locking and spatial hole burning are explained by taking halogenated
methanes (CH2BrI, CH2I2) as a model system.
The second chapter deals with the results of experimental studies
on “Orientation-selective Molecular Tunneling by Phase-controlled Laser
Fields”. After the basic properties of tunneling ionization (TI) of atoms
and molecules are introduced, the experimental results of directionally
asymmetric TI of CO, OCS, iodohexane, and bromochloroethane, which
are induced by ω + 2ω laser pulses, are presented.
The third chapter presents experimental and theoretical results of
“Reaction and Ionization of Polyatomic Molecules Induced by Intense
Laser Pulses”. The emphasis is on ionization rates, resonance effects,
dissociative ionization and Coulomb explosion of polyatomic molecules
v
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vi Advances in Multi-Photon Processes and Spectroscopy
such as cyclopentanone (C5H8O), which are induced by intense fs-laser
fields.
The fourth chapter presents the reviews of experimental studies on
“Ultrafast Internal Conversion of Pyrazine via Conical Intersection”.
Pyrazine is one of the typical azabenzenes undergoing ultrafast S2–S1 inter-
nal conversion through conical intersection. In this chapter, experimental
results of femtosecond internal conversion of pyrazine, that are observed
in real time using a time-resolved photoelectron imaging method with a
time resolution of 22 fs are presented. The method enables us to obtain a
time–energy map of the photoelectron angular anisotropy as well.
The fifth chapter deals with the theoretical studies of “Quantum
Dynamics in Dissipative Molecular Systems”. Dissipation is essential
in condensed phase systems. Femtosecond time-resolved spectroscopy
applied to photosynthetic antenna in proteins manifests as quantum beats,
which indicates the quantum nature of the system. The timescale of the
protein environment memory is found to be comparable to that of the energy
transfer. For such a system, traditional perturbative Markovian quantum
dissipation theories are inadequate. The reviews of theoretical studies in
the nonperturbative and non Markovian treatments are presented on the
basis of the hierarchical equation of motion approach.
The sixth chapter presents the results of the theoretical and computa-
tional studies of “First-principle Calculations for Laser Induced Electron
Dynamics in Solids”. Electron dynamics in a crystalline solid induced by
strong ultrashort laser pulses is totally different from that observed in atoms
and molecules. The basic principles and restrictions for treating electrons
in crystalline solids are described. Time-dependent Kohn-Sham equation
in a unit cell is solved based on the time-dependent density functional
theory. The present theory and computational method provide the most
comprehensive description for the interactions of strong and ultrashort laser
pulses with solids.
The editors wish to thank all the authors for their important contribu-
tions toAdvances in Multi-photon Processes and Multiphoton Spectroscopy
Vol. 21. It is hoped that the collection of topics in this volume will be
useful not only to active researchers but also to other scientists and graduate
students in scientific research fields such as chemistry, physics, and material
science.
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CONTENTS
Preface v
1. Vibrational and Electronic Wavepackets Driven
by Strong Field Multiphoton Ionization 1
P. Marquetand, T. Weinacht, T. Rozgonyi,
J. González-Vázquez, D. Geißler and L. González
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Theoretical Concepts . . . . . . . . . . . . . . . . . . 3
1.2.1 The time-independent Schrödinger equation
and its implications on dynamics . . . . . . . . 3
1.2.2 Spin-orbit coupling and diabatic vs.
adiabatic states . . . . . . . . . . . . . . . . . . 7
1.2.3 Nuclear time-dependent Schrödinger
equation . . . . . . . . . . . . . . . . . . . . . 9
1.2.3.1 Second-order differentiator . . . . . . . 11
1.2.3.2 Split-operator method . . . . . . . . . . 11
1.2.4 Stark shifts . . . . . . . . . . . . . . . . . . . . 13
1.2.5 Multi- vs. single-photon transitions . . . . . . . 15
1.2.6 Laser-dressed states . . . . . . . . . . . . . . . 19
1.2.7 Photon locking . . . . . . . . . . . . . . . . . . 20
1.2.8 Hole burning . . . . . . . . . . . . . . . . . . . 21
1.2.9 Strong-field ionization . . . . . . . . . . . . . . 23
1.3 Computational and experimental details . . . . . . . . 27
vii
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viii Advances in Multi-Photon Processes and Spectroscopy
1.4 Vibrational Wavepackets Created by Multiphoton
Ionization . . . . . . . . . . . . . . . . . . . . . . . . 29
1.4.1 Phase-dependent dissociation . . . . . . . . . . 29
1.4.1.1 Photon locking . . . . . . . . . . . . . 35
1.4.1.2 Hole burning . . . . . . . . . . . . . . 36
1.4.2 Ionization to different ionic states . . . . . . . . 38
1.4.2.1 Preparing electronic wavepackets
via SFI . . . . . . . . . . . . . . . . . 38
1.4.2.2 VMI measurements to identify
dissociation pathways following SFI . . 44
1.5 Conclusion and Outlook . . . . . . . . . . . . . . . . 49
References . . . . . . . . . . . . . . . . . . . . . . . . . . 50
2. Orientation-Selective Molecular Tunneling Ionization
by Phase-Controlled Laser Fields 55
H. Ohmura
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 55
2 Photoionization Induced by Intense Laser Fields . . . . 58
2.1 MPI in standard perturbation theory . . . . . . . 58
2.2 Keldysh theory: From MPI to TI . . . . . . . . 59
2.3 Characteristics of TI . . . . . . . . . . . . . . . 62
2.4 Molecular TI . . . . . . . . . . . . . . . . . . . 66
3 Directionally Asymmetric TI Induced by Phase-controlled
Laser Fields . . . . . . . . . . . . . . . . . . . . . . . 68
3.1 Phase-controlled laser fields . . . . . . . . . . . 68
3.2 Directionally asymmetric TI (atoms) . . . . . . 71
3.3 Directionally asymmetric TI (molecules) . . . . 75
4 Experimental . . . . . . . . . . . . . . . . . . . . . . 77
5 Results and Discussion . . . . . . . . . . . . . . . . . 83
5.1 Diatomic molecule: CO . . . . . . . . . . . . . 83
5.1.1 Photofragment detection . . . . . . . . 83
5.1.2 Photoelectron detection . . . . . . . . . 87
5.2 Other molecules . . . . . . . . . . . . . . . . . 92
5.2.1 Nonpolar molecule with asymmetric
structure: Br(CH2)2 Cl . . . . . . . . . 92
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Contents ix
5.2.2 Large molecule: C6H13I . . . . . . . . 94
5.2.3 Systematically changing molecular
system: CH3X(X=F, Cl, Br, I) . . . . . 96
5.2.4 OCS molecule investigated by nanosecond
ω + 2ω laser fields . . . . . . . . . . . 97
6 Summary . . . . . . . . . . . . . . . . . . . . . . . . 98
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 99
References . . . . . . . . . . . . . . . . . . . . . . . . . . 100
3. Reaction and Ionization of Polyatomic Molecules
Induced by Intense Laser Pulses 105
D. Ding, C. Wang, D. Zhang, Q. Wang, D. Wu and S. Luo
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 105
1.2 Ionization Rate of Molecules in Intense
Laser Fields . . . . . . . . . . . . . . . . . . . . . . . 110
1.2.1 Theoretical approaches for ionization rates of
molecules in intense laser fields . . . . . . . . . 110
1.2.2 Experimental measurements of ionization rates
of molecules and comparations with theory . . . 117
1.3 Fragmentation of Molecules in Intense Laser Fields . . 124
1.3.1 Ionization-dissociation of molecules in intense
laser fields and statistical
theoretical description . . . . . . . . . . . . . . 124
1.3.2 Effects of cation absorption on molecular
dissociation . . . . . . . . . . . . . . . . . . . 125
1.4 Dissociative Ionization and Coulombic Explosion
of Molecules in Intense Laser Fields . . . . . . . . . . 127
1.4.1 Dissociative ionization of formic acid molecules 128
1.4.2 Coulombic explosion of CH3I . . . . . . . . . . 131
1.5 Summary and Perspectives . . . . . . . . . . . . . . . 133
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 135
References . . . . . . . . . . . . . . . . . . . . . . . . . . 135