Vibrationally mediated photodissociation / Salman (Zamik) Rosenwaks.

Format:

Book

Author/Creator:

Rosenwaks, S. (Salman)

Language:

English

Subjects (All):

Photodissociation.

Vibration.

Molecular dynamics.

Gas dynamics.

Surfaces (Physics).

Physical Description:

xv, 204 pages : illustrations ; 24 cm

Place of Publication:

Cambridge, UK : Royal Society of Chemistry, [2009]

Summary:

Vibrationally Mediated Photodissociation (VMP) deals with the influence of vibrational excitation of the ground electronic state of a molecule on its dissociation following excitation of this state to a higher electronic state. Aimed at students and academics, this is the first book devoted to the effect of vibrational pre-excitation on molecular dynamics in the gas phase. In particular, it deals with the influence of this excitation on the dissociation of molecules (i.e. on the branching ratio between the dissociation products and its dependence on the vibrational state being excited). The effect in the gas phase has been extensively studied, both theoretically and experimentally and encompasses diverse areas of chemical physics.

This monograph presents the methodology of VMP, using state-of-the-art specific examples. Overviews of earlier works are included as well, to serve as a background for current research. Wherever appropriate, original works are quoted, including the original drawings. The contents include a brief review of theoretical and experimental methods relevant to VMP and specific examples. Also included are a bibliography, author and subject index. From the description of the motivation, the approach, the execution of the experiment and the analysis of the results of the specific examples, the reader will get a comprehensive understanding of the field.

The book is aimed at senior undergraduate and graduate students of chemistry and physics. It serves as an introduction to VMP for beginners and as a literature guide to those acquainted with the subject but not necessarily working on VMP.

Contents:

Chapter 1 Introduction 1

1.1 What is VMP and How Does it Work? 1

1.2 Why VMP? 4

1.3 Organization of the Monograph 6

References 7

Chapter 2 Theoretical Aspects 9

2.1 Photodissociation Dynamics 9

2.1.1 Potential-Energy Surfaces, the Born-Oppenheimer Approximation and the Franck-Condon Principle 10

2.1.2 Photodissociation Cross Sections: Computational Approaches 13

2.1.2.1 Classical Trajectories 14

2.1.2.2 Time-Independent Approach 14

2.1.2.3 Time-Dependent Approach 15

2.1.2.4 Comparison of the Time-Independent and Time-Dependent Approaches 18

2.1.3 Radiationless Transitions between PESs, the Role of Conical Intersections 18

2.1.4 Vector Correlations in VMP 20

2.2 Intramolecular Vibrational Dynamics: Normal and Local Modes and the Role of Intramolecular Vibrational Redistribution 21

2.2.1 Normal Modes and Local Modes 22

2.2.2 Intramolecular Vibrational Redistribution 23

References 27

Chapter 3 Experimental Methods 29

3.1 Preparation and Detection of Vibrational States 32

3.1.1 Nonspecific Vibrational Excitation 32

3.1.2 One-Photon, State-Selected Vibrational Excitation 32

3.1.3 Two-Photon, State-Selected Vibrational Excitation 33

3.1.3.1 Overtone-Overtone Double Resonance 33

3.1.3.2 Preparation by Stimulated Raman Excitation and Detection by Coherent Anti-Stokes Raman Spectroscopy and Photoacoustic Raman Spectroscopy 34

3.1.3.3 Preparation by Stimulated Emission Pumping 35

3.1.3.4 Preparation by Stimulated Raman Adiabatic Passage 35

3.1.4 Monitoring Vibrational Excitation 36

3.2 Excitation and Detection of Electronic States 36

3.3 Detection and Characterization of Photofragments 37

3.3.1 Spontaneous Emission and Laser-Induced Fluorescence 37

3.3.2 Resonantly Enhanced Multiphoton Ionization 37

3.3.3 Doppler Profiles 38

3.3.4 High-n Rydberg Time-of-Flight 38

3.3.5 Photofragment Translational Spectroscopy 39

3.3.6 Velocity-Map Imaging 40

References 40

Chapter 4 VMP of Diatomic Molecules and Radicals 43

4.1 HF 44

4.2 HCl 44

4.3 HBr 45

4.4 HI 46

4.5 OH, OD, SH and SD Radicals 47

4.6 O2 48

References 48

Chapter 5 VMP of Triatomic Molecules Excluding Water 51

5.1 VMP of O3 51

5.1.1 Spectral Features of O3 Relevant to VMP 51

5.1.2 VMP of O3 as a Source of O(1D) 53

5.1.3 Vector Correlations in the VMP of O3 54

5.2 VMP of OCS 55

5.2.1 Spectral Features of OCS Relevant to VMP 55

5.2.2 VMP of OCS in the Second and Higher Absorption Bands 55

5.2.3 VMP of OCS in the First Absorption Band 57

5.2.4 Vector Correlations in the VMP of OCS 59

5.3 OCSe 60

5.4 N2O 60

5.5 CS2 61

5.6 ICN 63

5.7 HCN, DCN, HOCl, DOCl and HOBr 63

References 64

Chapter 6 VMP of Water Isotopologues 68

6.1 Spectral and Dynamical Features of Water Relevant to VMP 68

6.2 VMP of H2O and HOD in the Second Absorption Band 70

6.3 VMP of H2O in the First Absorption Band 71

6.3.1 Vibrational-State Dependence of H2O Absorption Cross Section 71

6.3.2 Vibrational Distributions of the OH Photofragments 73

6.3.3 Rotational, Spin-Orbit and Λ-Doublet State Distributions of the OH Photofragments 75

6.3.3.1 Rotational Distributions 77

6.3.3.2 Spin-Orbit and Λ-Doublet Distributions 78

6.3.4 Vector Correlations in the VMP of H2O 79

6.3.5 VMP of H2O as a Spectroscopic Tool 79

6.4 VMP of HOD 81

6.4.1 VMP of HOD Pre-Excited to Fundamental OH or OD Vibrations 82

6.4.2 VMP of HOD Pre-Excited to OH Overtones 84

6.4.3 VMP of HOD Pre-Excited to OD Overtones 88

6.5 VMP of D2O 90

References 90

Chapter 7 VMP of Tetratomic Molecules 94

7.1 VMP of Acetylene Isotopologues 94

7.1.1 Spectral and Dynamical Features of Acetylene Relevant to VMP 94

7.1.2 VMP of C2H2 96

7.1.2.1 Adiabatic VMP of C2H2 97

(a) The 4vCH Region 97

(b) Comparison of VMP for Different Vibrational Levels in the 5vCH Region 97

(c) Rotational Effects in the 5vCH Region 101

(d) Comparison of VMP for Different Vibrational Levels in the 4vCH Region 103

(e) The 1vCH Region 104

7.1.2.2 Nonadiabatic VMP of C2H2 104

7.1.3 VMP of C2HD 107

7.1.3.1 Adiabatic VMP of C2HD-Evidence for Rotational Dependence of H/D Branching Ratio 107

7.1.3.2 Nonadiabatic VMP of C2HD 110

7.2 VMP of Ammonia Isotopologues 110

7.2.1 Spectral Features of Ammonia Relevant to VMP 110

7.2.2 VMP of NH3 111

7.2.2.1 VMP of NH3 Prepared at Low Vibrational Energies 111

7.2.2.2 VMP of NH3 Prepared at High Vibrational Energies 116

7.2.2.3 VMP of NH3 as a Spectroscopic Tool 117

7.2.3 VMP of NHD2 and NH2D 118

7.3 VMP of HNCO 120

7.3.1 Spectral Features of HNCO Relevant to VMP 120

7.3.2 A Brief Survey of the VMP of HNCO 121

7.3.3 Comparison of VMP of HNCO 3v1 to One-Photon Dissociation of Thermal Molecules 123

7.3.4 Application of VMP to HNCO Spectroscopy 128

7.4 VMP of Other Tetratomic Molecules 129

7.4.1 Hydrogen Peroxide Isotopologues 131

7.4.2 Nitrous Acid 134

7.4.3 Hydrazoic Acid 135

References 136

Chapter 8 VMP of Larger than Tetratomic Molecules 142

8.1 VMP of Methylamine Isotopologues 143

8.1.1 Spectral and Dynamical Features Relevant to VMP of Methylamine 143

8.1.2 VMP of CH3NH2 in the Region of the Fundamental CH3 and NH2 Stretches 145

8.1.2.1 Evidence for Mode-Dependent Enhancement of Bond Fission and Photoionization of CH3NH2 146

8.1.2.2 H-Atom Doppler Profiles: Evidence on the Main Photodissociation Channel 148

8.1.3 VMP of CH3NH2 in the Region of the NH2 Overtone Stretches 149

8.1.4 VMP of CD3NH2 150

8.2 VMP of Haloalkanes 151

8.2.1 Hydrochlorofluorocarbons 151

8.2.1.1 CHFCl2 152

(a) Enhanced Production of Photofragments 152

(b) Evidence for Vibrationally Induced Three-Body Photodissociation 153

8.2.1.2 CH3CFCl2 156

(a) Enhanced Production of Photofragments 156

(b) The Effect of Vibrational Pre-Excitation on the Branching Ratios of the Atomic Photofragments in the VMP of CH3CFCl2 and CH3CF2Cl 156

8.2.2 Methyl Iodide 157

8.2.2.1 Photodissociation in the First Absorption Band: General Background 157

8.2.2.2 Photodissociation of Vibrationally Excited CH3I 159

8.2.3 Other Haloalkanes 162

8.2.3.1 CF3I 163

8.2.3.2 CH3Cl and CHD2Cl 163

8.2.3.3 CH2Cl2 164

8.3 VMP of Phenol 164

8.4 VMP of Other Larger than Tetratomic Molecules 166

8.4.1 HONO2, (CH3)3COOH, CH3OH, NH2OH, HO2NO2 and CH3OOH 168

8.4.1.1 HONO2 ns and fs-ps VMP Studies 168

8.4.1.2 (CH3)3 COOH 169

8.4.1.3 CH3OH 169

8.4.1.4 NH2OH 170

8.4.1.5 HO2NO2 171

8.4.1.6 CH3OOH 172

8.4.2 Acetylene Homologues 172

8.4.2.1 Photodissociation Dynamics 173

(a) D3CC≡CH 173

(b) H3CC≡CH 174

(c) H3CH2CC≡CH 174

8.4.2.2 Applications to Vibrational Spectroscopy 176

8.4.3 Ethene Isotopologues 177

8.4.3.1 The Fourth C-H Stretching Overtone Region in H2C=CH2, Trans-HDC=CDH and H2C=CD2 178

8.4.3.2 Vibrational Patterns of the First Through Fourth C-H Stretching Overtone Regions in H2C=CH2 179

8.4.3.3 The First Stretch Overtone Region in Trans-HDC=CDH: Example of VMP-Based Detailed Analysis of Vibrational Spectroscopy and Dynamics 180

8.4.4 UF6 183

References 183.

Notes:

Includes bibliographical references and indexes.

ISBN:

9780854041558

0854041559

OCLC:

276224534