The field of viscous liquid and glassy solid dynamics is reviewed by a process of posing the key questions that need to be answered, and then providing the best answers available to the authors and their advisors at this time. The subject is divided into four parts, three of them dealing with behavior in different domains of temperature with respect to the glass transition temperature, Tg , and a fourth dealing with ‘‘short time processes.’’ The first part tackles the high temperature regime T.Tg ,i n which the system is ergodic and the evolution of the viscous liquid toward the condition at Tg is in focus. The second part deals with the regime T;Tg , where the system is nonergodic except for very long annealing times, hence has time-dependent properties ~aging and annealing!. The third part discusses behavior when the system is completely frozen with respect to the primary relaxation process but in which secondary processes, particularly those responsible for ‘‘superionic’’ conductivity, and dopart mobility in amorphous silicon, remain active. In the fourth part we focus on the behavior of the system at the crossover between the low frequency vibrational components of the molecular motion and its high frequency relaxational components, paying particular attention to very recent developments in the short time dielectric response and the high Q mechanical response. © 2000 American Institute of Physics.@S0021-8979~00!02213-1#

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1065&context=mse_pubs

Relaxation in glassforming liquids and amorphous solids

https://hal.archives-ouvertes.fr/hal-00120432/document

Raman Spectroscopy of Nanomaterials: How Spectra Relate to Disorder, Particle Size and Mechanical Properties

Raman spectroscopy studies of alkali and alkaline earth silicate glasses and melts are reviewed, and the major Raman bands observed are summarized. To realize the full potential of Raman spectroscopy will require a detailed understanding of their vibrational properties in relation to structure. A number of vibrational calculations have been carried out to address this problem. These are briefly summarized, and some limitations of the method are noted. Systematic variations in bulk properties are examined for viscosity and the immiscibility behavior.

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Structural studies of silicate glasses and melts—applications and limitations of Raman spectroscopy

Optical nonlinearities in the context of lightwave systems limitations are described. The nature and severity of system degradation due to stimulated Raman scattering, carrier-induced phase noise, stimulated Brillouin scattering, and four-photon mixing are discussed. The system power limitations are plotted as a function of a number of wavelength-multiplexed channels. Methods for scaling these results with changes in system parameters are presented. >

Limitations on lightwave communications imposed by optical-fiber nonlinearities

We report on the micro-Raman spectroscopy of monolayer, bilayer, trilayer, and many layers of graphene (graphite) bombarded by low-energy argon ions with different doses. The evolution of peak frequencies, intensities, linewidths, and areas of the main Raman bands of graphene is analyzed as function of the distance between defects and number of layers. We describe the disorder-induced frequency shifts and the increase in the linewidth of the Raman bands by means of a spatial-correlation model. Also, the evolution of the relative areas ${A}_{D}/{A}_{G}$, ${A}_{{D}^{\ensuremath{'}}}/{A}_{G}$, and ${A}_{{G}^{\ensuremath{'}}}/{A}_{G}$ is described by a phenomenological model. The present results can be used to fully characterize disorder in graphene systems.

Evolution of the Raman spectra from single-, few-, and many-layer graphene with increasing disorder

We present a calculation of the dielectric correlation function in glasses showing how the assumption of short correlation length for normal modes breaks the momentum selection rules and leads to expressions for the first-order Raman-scattering intensity in terms of the density-of-states functions and known frequency-dependent amplitudes

Raman-Scattering Selection-Rule Breaking and the Density of States in Amorphous Materials

Laser light sources and sensitive photoelectric detection allow the present day experimenter to obtain crystal Brillouin scattering spectra for well defined scattering vector directions and completely polarized incident and scattered radiation. Thus we now have a very powerful tool for exploring the elastic and photoelastic anisotropy in crystals from a combination of measurements of the frequency shifts of the components and the intensities of the components in polarized spectra.

Robert W. Gammon

Papers

Raman-Scattering Selection-Rule Breaking and the Density of States in Amorphous Materials

Examples of Crystal Brillouin Scattering Polarization Selection Rules