Showing papers on "Depolarization ratio published in 1976"

Dependence of Bandshape and Depolarization Ratio on Slitwidth

Abstract: A simple correction formula is presented for obtaining true Lorentzian half-bandwidths from convolutions with triangular slits. The correction is shown to be applicable to a number of other convolutions. Also, the dependence of the depolarization ratio in terms of peak heights on slitwidth is investigated.

New values of the light scattering depolarization and anisotropy of water

Abstract: A new value for the depolarization ratio of pure water has been measured at 514.5 nm using an argon ion laser light source and photon counting detection. This depolarization ratio is lower than any previous literature value by a substantial amount. Stray light and photometer geometry are shown to be responsible for overestimated values reported previously. The depolarization ratio is also shown to be a function of the portion of the spectrum being investigated. With no filters we find ρv=0.026. The magnitude of error due to finite acceptance angle is calculated and shown to be substantial. Depolarization ratios using 0.46 and 22.5 nm filters (half‐peak bandwidth) are reported.

Study of polymerizing styrene through depolarized light scattering

Abstract: The thermal polymerization of clean styrene has been studied through Rayleigh-Brillouin light scattering. The frequency shifts, Rayleigh to Brillouin intensity ratios, Rayleigh depolarization ratios, and depolarized intensities were measured as the polymerization proceeded to completion at 90°C. The depolarized intensities decreased and the frequency shifts increased smoothly from the monomer to the polymer values. The Vv intensities and Rayleigh to Brillouin intensity ratios increase dramatically during the first stages of polymerization then decrease systematically to their final values. There is a large increase in the Rayleigh to Brillouin intensity ratio from the monomer to the final polymer value. The vertical depolarization ratio pv and the horizontal depolarization ratio pV were found to be respectively 0.4 and 1 for the polymer. Our observations are explained in terms of light being scattered from concentration fluctuations in the early stages of polymerization and from spherically symme...

Depolarization dispersion of a fundamental line of a totally symmetric vibration in resonance Raman scattering

Abstract: Vibronic coupling of the Herzberg-Teller type is discussed as a possible source of the depolarization dispersion of a fundamental line of a totally symmetric vibration in resonance Raman scattering (RRS). Two cases are discussed separately. The first case concerns RRS from an electronic state that borrows part of its intensity from a non-overlapping electronic state of different symmetry. In this case the depolarization ratio of the fundamental line for right angle scattering linearly polarized light can vary between the limits 1/8 and 3/4. The second case arises when part of the intensity is borrowed from an electronic state of the same symmetry but with a transition moment non-parallel to that of the resonant state. Such a situation can occur in molecules with a symmetry corresponding to one of the following point groups: C1, Ci, C2, Cs, C1h, C2h, S2. In this situation the depolarization ratio ρl can vary between the limits 1/8 and. In both cases the amplitude of the variations of ρl depends on the damping constant. In the second case the value of the displacement parameter of a totally symmetric mode has a major influence on the range of change of ρl. Both cases show prominent resonance-antiresonance coincidences between depolarization dispersions and excitation profiles, which has been previously predicted for non-totally symmetric modes, and for molecular dimers. It is pointed out that the depolarization ratio in the preresonance region is very sensitive to vibronic coupling and can serve as a probe of such coupling.

Frequency Dependence of Relative Intensities and Depolarization Ratio for Resonance Raman Scattering

Abstract: Theoretical expressions for the frequency dependence of the intensities of Raman lines in the pre-resonance and rigorous resonance Raman scattering are derived on the basis of a new approach. In this effort the main contribution to the change in polarizability is obtained from the derivative of electronic transition moment with respect to the vibrational normal coordinates. Therefore, this approach differs from previous approaches which suggested that the main contribution to the Raman intensities (polarizability derivative) comes from the derivative of electronic frequency with respect to the normal coordinate. This new approach leads to excellent agreement between the derived theoretical expressions and several recently reported experimental studies. In this paper the effective absorption frequencies and damping terms are determined from the excitation profile rather than the electronic absorption spectrum. To extend these studies to non-totally symmetric modes by considering the scattering due to nondiagonal polarizability tensor components, we have attempted to derive the depolarization ratios by calculating the contribution to the scattered intensity from the quadrupole and magnetic dipole terms. An anomalous depolarization ratio results from the angular distribution of the magnetic dipole vibration at a certain spectral location.

On the value of the depolarization ratio of fundamentals of sandwich compounds with an electronically degenerate ground state

Abstract: The selection rules are derived for the Raman activity of fundamental modes in electronically degenerate groundstates of sandwich compounds. Emphasis is placed on the occurrence of asymmetric tensors, which can result in values of the depolarization ratio of Raman bands larger than 3/4.