W. F. Murphy

The Rayleigh depolarization ratio and rotational Raman spectrum of water vapor and the polarizability components for the water molecule

This paper describes the observation and computer simulation of the rotational Raman spectrum of water vapor and the measurement of the depolarization ratio for Rayleigh scattering from water vapor, which was found to be (3.0±1.4) ×10−4. These results were combined with the value of the mean polarizability to calculate the principal polarizability components of the water molecule. At 514.5 nm, they are (in units of 10−24 cm3): αxx=1.468±0.003, αyy =1.415±0.013, and αzz=1.528±0.013, where the x axis is the dipole axis and the y axis is perpendicular to the molecular plane.

Resonance Raman Effect and Resonance Fluorescence in Halogen Gases

The various output frequencies of the argon ion laser at 5145, 5017, 4965, 4880, and 4765 A lie in the absorption bands of the heavier halogen gases. With the appropriate choice of exciting line, either resonance Raman effect or resonance fluorescence can be observed. The difference between the two types of spectra are discussed in some detail. In the case of a strong resonance Raman effect, overtone sequences up to the 14th harmonic could be observed. Raman frequencies, depolarization ratios, and relative scattering cross sections are given for the fundamentals and overtones of Cl2, Br2, I2, BrCl, ICI, and IBr at 4880 A excitation.

Gas Phase Raman Intensities: A Review of “Pre-Laser” Data

Raman radiant intensities and depolarization ratios measured for gases with mercury arc irradiation and photoelectric detection have been collected. The observed intensities have been reduced to values of the scattering activity, gj(45α j ′2+7γ j ′2). The scattering activity and Raman scattering cross sections are explicitly related. Data for strong sharp bands are accurate to about ± 5% – 10%, while data for weak and broad bands are less accurate.

Rotational isomerism. XI. Raman spectra of n‐butane, 2‐methylbutane, and 2, 3‐dimethylbutane

Raman spectra have been obtained for n‐butane, 2‐methylbutane, and 2, 3‐dimethylbutane in the vapor and solid (−196°C) phases. The low temperature spectra of the solids undergo a marked simplification due to the disappearance of all but one of the rotational isomers. This enabled band pairs in the vapor spectrum to be identified with the appropriate rotational isomers. From the temperature dependence of selected band pairs the enthalpy difference between the rotational isomers was obtained for each compound in the vapor phase.

Isolated C–H stretching vibrations of n‐alkanes: Assignments and relation to structure

The conformational/configurational dependence of the frequencies of the deuterium‐isolated C–H stretching modes of the gas‐phase alkanes C1, C2, n‐C3, n‐C4(t and g), n‐C5(tt and gt), cyclo‐C6, iso‐C4, and neo‐C5 are reported. Most of the isolated C–H frequencies were obtained from Raman spectra of specifically and randomly protonated deuterohydrocarbons. An extraordinarily precise correlation is found between the observed isolated C–H frequencies and the corresponding ab initio calculated C–H bond lengths. In the case of the n‐alkanes, the observed C–H frequencies tend to fall in clusters that are regularly spaced with an average separation of about 14.5±1 cm−1. The clustering occurs because the isolated C–H stretching frequencies are determined by the structure of the n‐alkane in the immediate vicinity of the C–H bond. The relation between frequency and local structure can be expressed in a simple way and used to predict the effect of conformational change.

The rovibrational Raman spectrum of water vapourv1andv3

The OH stretching region in the Raman spectrum of water vapour has been observed and reproduced by computer simulation using rovibrational wave functions derived from the analysis of high-resolution absorption spectra. Relative intensity measurements allow the determination of the depolarization ratio and the ratio of the two non-vanishing second-order irreducible tensor components for v 1. These quantities have been combined with the literature value for the cross section of this band to calculate the principal cartesian components of the v 1 derived polarizability tensor. The cross section for the v 3 vibration was also determined, and these results are considered in terms of the bond polarizability theory.

Raman spectra of negative molecular ions doped in alkali halide crystals

Abstract Raman bands arising from S 2 − and S 3 − have been observed in alkali halide single crystals which had been heated in the presence of sulphur vapor. The S 3 − ion could also be detected in the mineral ultramarine. Since the excitation frequency was sometimes close to the absorption band of these species, a resonance Raman effect was observed. This was strongest for the S 3 − species in KCl where the fifth overtone of the symmetrical stretching mode vibrational could be seen. In similarly treated crystals, the vibrational Raman bands of Se 2 − and SeS − were observed. Raman data for N 2 − in potassium halide single crystals are also reported.

The ro-vibrational Raman spectrum of water vapour υ2 and 2υ2

Weak spectral features in the Raman spectrum of water vapour associated with the v 2 and 2v 2 vibrations have been observed. These features have been reproduced by computer simulation using the results of high resolution absorption spectral analyses. Relative intensity measurements allow the determination of the cross section, depolarization ratio and ratio of the two non-vanishing second-order irreducible spherical tensor components for v 2. From these quantities, the principal components of the v 2 derived polarizability tensor have been determined, and these results, as well as the mean derived polarizability tensor for the 2v 2 transition, are considered under the bond polarizability theory.

Pressure effects on the Raman spectra of phospholipid membranes: Pressure induced phase transitions and structural changes in 1,2‐dimyristoyl 3‐sn‐phosphatidylcholine water dispersions

In a study of the pressure dependence of the Raman spectrum of an aqueous dispersion of dimyristoyl phosophatidylcholine from ambient pressure up to 5 kbar, three phase transitions have been observed at 150 bar and at 1 and 2.6 kbar. From the behavior of the spectrum, a correlation may be made between these phase transitions and temperature‐induced changes observed at 24, 14, and −60 °C, respectively. The major cause of the pressure‐induced frequency shift of all the Raman bands is the pressure‐enhanced interchain anharmonic interaction rather than the pressure‐induced compression of intramolecular bonds. It is further shown that the large angle reorientational fluctuations about the long axes of the acyl chains decrease with increasing pressure.

Raman and Rayleigh spectroscopy and molecular motions

Extensive measurements of vibrational and, in a few cases, pure rotational Raman spectra of HCl, DCl, HBr and DBr dissolved in SF6, C2F6, CCl4 and SO2 have been carried out at room temperature. Band profiles of both isotropic and anisotropic scattering have been studied and discussed in the light of existing theories on molecular motions in liquids. From isotropic scattering band-fitting it is concluded that, in the case of the three non-polar solvents, broadening due to vibrational fluctuations is small and that the band shape comes essentially from vibration-rotation coupling. Thus information about reorientational motions can be obtained directly from anisotropic scattering. For SO2 solutions this statement is no longer valid because of the important contribution of vibrational fluctuations to the profile of the isotropic scattering. In this case the rotational correlation function can be determined, as for pure liquid hydrochloric and hydrobromic acids, by elimination of the vibrational correlation fu...