CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

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CHAPTER 5 UV-Vis Spectra of Anionic Hydrated Clusters: Extrapolation to Bulk 5.1. Introduction Recently, a few attempts are being made to reproduce the bulk properties, like detachment energies of the excess electron of bulk solute solution (aqueous) from the knowledge of finite size anionic hydrated cluster data applying size selected photoelectron spectroscopy. 9,33-35 UV-Vis spectra of many transients in aqueous solution (bulk) are widely applied to study complex chemical reaction. However, no effort is made to connect UV-Vis spectra of a solute in aqueous solution to that of its finite size hydrated clusters. In this regard, hydrated clusters of Cl • 2 ⎯, Br • 2 ⎯, I • 2 ⎯ and CO • 3 ⎯ are studied following first principle based theoretical methods to understand the origin of UV-Vis transition and to extract bulk optical absorption spectra of these radical anions in their respective aqueous solution. This study is very useful to those who practice radiation chemistry. In aqueous solution, hydroxyl radical ( • OH) reacts with X¯ (X=Cl, Br &I) to form a transient species, which has a broad and strong absorption in the UVvisible region. 3,59 This absorption maximum is assigned to the halogen dimer radical anion species, X 2•¯( X=Cl, Br &I), a specific one electron oxidising species. It is reported that Cl 2•¯, Br 2•¯ and I 2•¯ species absorb strongly in their respective aqueous solution with absorption maximum (λ max ) at 340, 360 and 380 nm, respectively. Similarly, hydroxyl 84
adical ( • OH) reacts with HCO 3¯ or CO 32¯ to form a transient species, which has a broad and strong absorption in the visible region with absorption maximum, λ max at 600 nm. This absorption maximum is assigned to the carbonate radical anion species, CO 3•¯, a specific one electron oxidising species. 60 In this chapter, results of chlorine dimer radical anion (Cl 2•¯) and carbonate radical anion species (CO 3•¯) are presented in detail. Simulated UV-Vis spectra of Cl 2•¯ and CO 3•¯ hydrated clusters are compared with the reported experimental transient optical absorption spectra of Cl 2•¯ and CO 3•¯ species in aqueous solution and electronic transitions responsible for the optical absorption spectra of Cl 2•¯(aq) and CO 3•¯ are also assigned based on studies of excited states. 5.2. Theoretical Approach As it is discussed in chapter 2, quasi Newton Raphson based algorithm is applied to carry out geometry search in each of hydrated clusters with various initial structures designed systematically following bottom-up approach to find out the most stable equilibrium structure. This procedure involves the calculation of a multi-dimensional potential energy surface for these clusters and finding a minimum on the surface. The key issue in this search procedure is to guess a good initial geometry of the cluster, which might converge during the calculation to a local or the global minimum. It is to be noted that the adopted procedure for geometry search cannot guarantee to locate the global minimum. Thus simulated annealing combined with Monte-Carlo sampling method has also been applied to search for the global minimum energy structure for each size clusters. 36 In this method, molecular coordinates have been displaced by a random amount and the energy of the system has been evaluated at the new structure. The new 85
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MICROSOLVATION OF CHARGED AND NEUTR
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STATEMENT BY AUTHOR This dissertati
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Dedicated to my Daughter, Wife and
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CONTENTS Page No. SYNOPSIS LIST OF
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CHAPTER 4 Solubility of Halogen Gas
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7.3.4. IR and Raman Spectra 117-121
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S Macroscopic Microscopic Dual leve
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molecular level interaction during
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Chapter 3: This chapter describes I
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In this system the conformers of a
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LIST OF FIGURES Page No. Fig. 1.1 2
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Fig. 2.6 54 (I) Plot of calculated
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(IIIA) Cl 2 .3H 2 O; (IIIB) Br 2 .3
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Fig. 6.3 104-105 Calculated scaled
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LIST OF TABLES Page No. Table. 2.1
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CHAPTER 1 Introduction 1.1. Microso
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1.2. Motivation 1.2.1. Macrosolvati
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ulk water and pure neutral water cl
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insight about the electronic struct
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Newton -Raphson (NR) method expand
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potential energy surface for these
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terms, the energy can be written in
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Boyd proposed the use of Gaussian t
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eported experimental findings. Theo
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hydrated halide series, X¯.nH 2 O,
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anions (Cl •− 2 , Br •− 2 &
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geometrical parameters close to MP2
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symmetrical DHB, SHB or WHB arrange
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of I-I axis and having the least I-
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Br •− 2 .nH 2 O hydrated cluste
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VI-F VI-G VII-A VII-B VII-C VII-D V
Page 63 and 64: To see the effect of hydration on t
Page 65 and 66: Five minimum energy structures disp
Page 67 and 68: arrangements. In total, it has one
Page 69 and 70: NO 3 − .nH2 O (n ≥ 6), a few eq
Page 71 and 72: V-E V-F V-G V-H V-I VI-A VI-B VI-C
Page 73 and 74: VII-D VII-E VII-F VII-G VII-H VII-I
Page 75 and 76: VIII-K VIII-L Fig.2.2. Fully optimi
Page 77 and 78: clusters. Hydrated cluster having c
Page 79 and 80: However, these calculations do not
Page 81 and 82: Table 2.1. Weighted average energy
Page 83 and 84: Where, E[I •− 2 .nH 2 O] is the
Page 85 and 86: The variation of the weighted avera
Page 87 and 88: CHAPTER 3 IR Spectra of Water Embed
Page 89 and 90: ecome more meaningful. At present,
Page 91 and 92: I-A II-A II-B III-A III-B III-C III
Page 93 and 94: Cluster experiments are carried out
Page 95 and 96: 3350-3500 cm -1 (scaling factor ~0.
Page 97 and 98: these systems, X. nH 2 O (X= Br 2
Page 99 and 100: CHAPTER 4 Solubility of Halogen Gas
Page 101 and 102: including polarized and diffuse fun
Page 103 and 104: and I 2 systems. The most stable st
Page 105 and 106: Cl Cl Br Br I I VA VB VC Cl Cl Br B
Page 107 and 108: (Br δ+ -Br δ- ) in the studied hy
Page 109 and 110: stabilization energy does not follo
Page 111 and 112: 80 Cl 2 .nH 2 O (n=1-8) 80 Br 2 .nH
Page 113: separated ion pair in presence of s
Page 117 and 118: most stable conformer for each size
Page 119 and 120: The structures of the hydrated clus
Page 121 and 122: Table 5.1. Calculated absorption ma
Page 123 and 124: molar extinction coefficient value
Page 125 and 126: ammonia. 61-62 Hydrogen bonded wate
Page 127 and 128: stable minimum energy structure is
Page 129 and 130: IV-A IV-B V-A V-B V-C VI-A VI-B VI-
Page 131 and 132: 6.3.3. Vertical Ionization Potentia
Page 133 and 134: 311++G(2d,2p) level, the scaling fa
Page 135 and 136: K(NH 3 ) 4 K(NH 3 ) 5 IR Intensity
Page 137 and 138: CHAPTER 7 Structure, Energetics and
Page 139 and 140: Thus Monte Carlo based simulated an
Page 141 and 142: I I I I I I I I A B C D I I I I I I
Page 143 and 144: interaction as well as solvent-solv
Page 145 and 146: Table 7.1. Various energy parameter
Page 147 and 148: change in VDE is observed. This is
Page 149 and 150: symmetric C-O stretching mode of CO
Page 151 and 152: to the maximum charge transfer of t
Page 153 and 154: CHAPTER 8 A Generalized Microscopic
Page 155 and 156: possible breakdown of these laws ma
Page 157 and 158: P 7 P , , P , ,, 1 ∂ 2
Page 159 and 160: M DE = (r, ω)C DE , (r,
Page 161 and 162: known. However, for most of the com
Page 163 and 164: The calculated bulk detachment ener
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espect to experimentally measured v
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References 1. Ohtaki, H.; Radani, T
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29. Turi, L.; Sheu, W.; Rossky,P.J.
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61. (a) Ehrler, O. T.; Neumark, D.
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LIST OF PUBLICATIONS *1. “σ/σ
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13. “Vibrational analysis of I
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CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

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