Dipole orientation, stretch bands

Much attention has been given to the analysis of OH stretching bands of micas occurring in an isolated region of the spectrum ranging from about 3750 to 3550 cm (Farmer 1974). Using polarized radiation, the pleochroic scheme of IR absorption bands, measured on oriented crystal sections, makes it possible to impose defined constraints on the orientation of the OH dipoles. In a fundamental polarised IR study, Tsuboi (1950) determined the position of the H atom in the structure of muscovite. The variation of absorption intensity of the OH stretching band with the direction of the electric vector of... 

Dipole reorientation under the influence of an electric field was investigated in oriented nylon 11 films with polarised IR spectroscopy for the amide A (N-H stretching) and amide I (carbonyl stretching) bands. Butterfly-shaped hysteresis loops were obtained from peak intensity versus applied electric field strength. Least-squares Gaussian... 

Chapter 3 is devoted to dipole dispersion laws for collective excitations on various planar lattices. For several orientationally inequivalent molecules in the unit cell of a two-dimensional lattice, a corresponding number of colective excitation bands arise and hence Davydov-split spectral lines are observed. Constructing the theory for these phenomena, we exemplify it by simple chain-like orientational structures on planar lattices and by the system CO2/NaCl(100). The latter is characterized by Davydov-split asymmetric stretching vibrations and two bending modes. An analytical theoretical analysis of vibrational frequencies and integrated absorptions for six spectral lines observed in the spectrum of this system provides an excellent agreement between calculated and measured data. 

Horswell et al. [80] made the first attempt to apply PM IRRAS to determine tilt angles of acyl chains of DM PC in a bilayer of this phospholipid deposited at an Au(lll) electrode surface in 2002. No correction of the measured spectra for the PEM response function was made at that time, and the tilt angle was determined using the relative method. It was assumed that the transition dipole of the asymmetric VaslCHs) stretch was randomly oriented. The tilt angle was then calculated from the ratio of the integrated intensity of the asymmetric Vas(CH2) and symmetric Vs(CH2) methylene stretches to the integrated intensity of the Vas(CH3) band using Eq. (43). 

---