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CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

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CHAPTER 3<br />

IR Spectra of Water Embedded Anionic Clusters<br />

3.1. Introduction<br />

Recently, size selected gas-phase infrared (IR) cluster spectroscopy combined<br />

with first principle based theoretical studies are being successfully applied to explore the<br />

molecular level interaction during the process of microhydration. Theoretical analysis of<br />

the observed IR band in the O-H stretching region of water of a particular cluster have<br />

yielded an understandable picture of how hydrogen bonding water networks are<br />

deformed when they attach to small solute anions. 7-8,23 IR spectra of size selected cluster<br />

are being widely applied to understand the geometry and growth motif of various<br />

chemical species during the process of microhydration. In this context, mostly spherical<br />

halide anions (F⎯, Cl⎯, Br⎯ and I⎯) are studied. 7-8<br />

Microhydration of diatomic and<br />

polyatomic species like OH⎯, O 2 ⎯, NO •− , SO 2 4 ⎯, etc are also studied based on IR<br />

spectroscopy. 8,15,23,25-26 It is understood from the studies that the smaller size solute –<br />

water cluster is stabilized by single (SHB) or double hydrogen bonding (DHB) and inter<br />

water hydrogen bonding (WHB). In the larger cluster the water network form cyclic<br />

arrangement to stabilize a particular cluster.<br />

In this chapter, IR spectra of halogen dimer radical anions (Cl •− 2 , Br •− 2 & I •− 2 ),<br />

carbonate radical anion (CO •− −<br />

3 ), nitrate anion (NO 3 ) and carbonate anion (CO 2− 3 )<br />

systems have been studied by first principle based electronic structure methods to<br />

57

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