Water fundamental vibration modes

Figure 1. Fundamental vibration modes of a water molecule.

A nonlinear molecule with n atoms generally has 3n — 6 fundamental vibrational modes. Water (3 atoms) has 3(3) -6 = 3 fundamental modes, as shown in the preceding figure. Methanol has 3(6) - 6 = 12 fundamental modes, and ethanol has 3(9) - 6 = 21 fundamental modes. We also observe combinations and multiples (overtones) of these simple fundamental vibrational modes. As you can see, the number of absorptions in an infrared spectrum can be quite large, even for simple molecules. 

A nonlinear molecule with n atoms generally has 3n — 6 fundamental vibrational modes. Water (3 atoms) has 3(3) — 6 = 3 Fundamental modes, as shown in the preced-... 

FIGURE 63 Some fundamental vibration modes for water. 

In the following we present results on fundamental vibrational transitions of isolated AT base pairs microsolvated with 1-4 water molecules. The aim of this study is twofold First to find out about overall changes of IR transitions of base pair modes due to the interaction with water molecules. And, second, to test the performance of a dual level approach combining density functional (DFT) and semiempirical PM3 data to expand the PES. Throughout we will assume that the deviations from equilibrium structures are small enough such... 

Fundamental vibrations involve no change in the center of gravity of the molecule. The three fundamental vibrations of the nonlinear, triatomic water molecule are depicted in the top portion of Figure 2.1. Note the very close spacing of the interacting or coupled asymmetric and symmetric stretching compared with the far-removed scissoring mode. 

Hydroxygermylene, HGeOH, was first produced in Ar matrix at 15 K upon photoin-duc (340-300 nm) intramolecular insertion of Ge atom into the OH bond of H2O submolecule in a Ge OH2 complex, formed by co-deposition of Ge atoms and water with excess Ar . Three observed IR bands at 1741.3, 661.3 and 566.2 cm were assigned to Ge OH stretching, Ge—O stretching and torsion vibrational modes. Later, HGeOH was identified as one of the products of the photochemical reaction of GeELj with O3 in Ar matrices. AU the fundamental frequencies of this molecule [vi(OH) = 3652.0,... 

The IR and Raman spectra of partially hydrated proteins are a rich source of fundamental information on both water and protein species, owing to the sensitivity of vibrational modes to hydrogen bonding. The similar chemistry of water—water and water—peptide interactions requires that there be great accuracy in spectroscopic measurements of the hydration process. Since the review of the field by Kuntz and Kauz-mann (1974), the Fourier transform technique for IR and the tunable laser for Raman spectroscopy have offered important improvements in methodology. 

The motion of a water molecule may be described in terms of two components (i) the motion of the center of mass of the entire molecule (this includes both translation and rotations) and (ii) the relative motions of the atoms within the molecule. The latter may be described in terms of three fundamental ( normal ) modes of vibration (see Fig. 1.2). 

Of particular importance is a strong band in the spectrum of aliphatic alcohols usually located near 1060 cm. This absorption has been identified as the C—O stretching mode. The vibrational displacements of this fundamental are similar to the antisymmetric stretch of water (see Chapter 8W for a detailed discussion of the vibrational modes of the water molecule). Since the vibration involves significant displacement of the adjacent C—C oscillator, the vibration wiU be substitution sensitive. These latter shifts can be of value in determining the nature of the alcohol (primary, secondary, or tertiary, see Table 8.9). 

Phase separation and spatial organization of membrane domains determine the state of water, fundamental interactions in the polymer/water/ion system, vibration modes of fixed sulfonate groups, and mobilities of water molecules and protons. Dynamic properties of the membrane can be probed at the microscopic scale with spectroscopic techniques, including Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) (Mauritz and Moore, 2004). FTIR... 

Equations 6.1-6.3 show that energy transitions are allowed for certain multiples of a fundamental frequency. In this case, energy transitions occur between nonadjacent energy levels and are usually named overtones. Similarly, multiple energy transitions can occur simultaneously in complex molecules, where different fundamental rotational and vibrational modes are possible. These complex energy transitions are usually called combinations [25, 27]. Figure 6.3 illustrates these concepts for the simple water molecule. As overtones and combinations involve larger... 

The water molecule has three normal modes of vibration, and therefore three fundamental frequencies symmetric stretching (r ), bending ( 2), and asymmetric stretching (1 3). The positions of the bands corresponding to these three vibrational modes in the gas phase and in the liquid phase are... 

FIG. 9 Vibrational sum frequency spectrum in the OH mode region of the neat air-water interface at different temperature for the fundamental visible and infrared beams respectively s- and p-polar-ized and the SFG beam s-polarized. (From Ref. 120, copyright American Physical Society.)... 

---