Thermal, structural, and orientational relaxation of supercooled salol studied by polarization-dependent impulsive stimulated scattering

Abstract

On the mechanism of reorientational and structural relaxation in supercooled liquids: The role of border dynamics and cooperativity Impulsive stimulated thermal scattering study of structural relaxation in supercooled glycerol Time-resolved transient grating experiments with various polarizations are used to separate different responses and measure their dynamics in supercooled liquid salol. A contribution to signal from orientational alignment induced by flow that arises from thermal expansion is demonstrated. This contribution is distinct from that due to orientational alignment induced directly by the excitation light through the molecular polarizability anisotropy ͑i.e., through the optical Kerr effect͒. It is also distinct from signal contributions due to density modulations induced by thermal expansion. The results offer additional insight into salol dynamics and into time-dependent transient grating measurements of this class. Depending on the light polarizations used, any of the signal contributions can be eliminated or highlighted.

α-Scale decoupling of the mechanical relaxation and diverging shear wave propagation length scale in triphenylphosphite

“…We conclude by noting that orientational responses of anisotropic molecules can be induced not only by the excitation pulses, as in the case of OKE, but also by flow that occurs due to the induced density changes [40]. Both of these sources lead to signals that can be suppressed by proper selection of probe and signal polarizations.…”

“…A full treatment of signal in an ISS experiment includes longitudinal and transverse acoustic modes, molecular orientations, and other nonoscillatory degrees of freedom [14,[35][36][37][38][39][40]. Here, we present a slightly simplified derivation that allows us to understand the presence of shear and orientational contributions to the signals.…”

Thermoelastic Model for Impulsive Stimulated Scattering Monitoring the Evolution from Capillary to Rayleigh Type Wave Propagation on the Surface of Viscoelastic Materials Throughout the Glass Transition

“…When polarization selective detection is done, even information about the rotational relaxation can be extracted [7]. Also, in the reflection mode, the signal-to-noise ratios achieved by ISS in the heterodyne detection mode are quite satisfactory [1,2,28,31], even for rough samples [32].…”

“…The impulsivestimulated scattering (ISS) method [1] has been successfully used to simultaneously investigate the thermal and elastic properties of materials in a four-wave mixing configuration, both in transmission in semitransparent materials and on reflecting surfaces of solids [2,3]. The ISS technique has shown to be quite effective to characterize the structural relaxation and longitudinal acoustic behavior in glass formers [4][5][6][7][8][9] in the MHz to GHz range. ISS in the transmission configuration also allows one to excite, via the Kerr effect, and to detect, via the detection of depolarized impulsive scattering, shear acoustic waves, but the approach is not effective in the lower MHz range.…”

Determination of elastic properties of a MnO2 coating by surface acoustic wave velocity dispersion analysis

“…ISTS has successfully been used to study SAW behavior and to probe material characteristics for a number of different configurations, in both solid and liquid materials. Characterization of bulk solids and liquids, [10][11][12][13] the study of acoustic waves at interfaces 14,15 and the investigation of thin (un)supported films 16,17 are just a few examples.…”