Surrogate for Debye–Waller Factors from Dynamic Stokes Shifts

Abstract

We show that the short-time behavior of time-resolved fluorescence Stokes shifts (TRSS) are similar to that of the intermediate scattering function obtained from neutron scattering at q near the peak in the static structure factor for glycerol. This allows us to extract a Debye-Waller (DW) factor analog from TRSS data at times as short as 1 ps in a relatively simple way. Using the time-domain relaxation data obtained by this method we show that DW factors evaluated at times ≥ 40 ps can be directly influenced by α relaxation and thus should be used with caution when evaluating relationships between fast and slow dynamics in glassforming systems.

Roles of chain stiffness and segmental rattling in ionomer glass formation

“…Specifically, the generalized localization model (GLM) of supercooled liquid dynamics, rather than attempting to directly model the temperature‐dependence of τ α on T , as does the Adam–Gibbs theory, focuses on understanding the relationship between τ α and high‐frequency rattling dynamics as quantified by the Debye–Waller factor 〈 u 2 〉. In terms of experimental applicability, this is an attractive theoretical framework because both τ α and 〈 u 2 〉 are experimentally accessible quantities; the former can be measured via neutron scattering and dielectric spectroscopy, for example, and the latter via neutron scattering, Mossbauer scattering, and time‐resolved Stokes‐shift spectroscopy . The GLM specifically predicts that these two quantities are related through the equation: where τ A and are the values of τ α and 〈 u 2 〉 at the onset temperature T A of glass formation and α is a fitting parameter that within the GLM is interpreted as being related to the anisotropy of local segmental rattle volume.…”

“…Specifically, recent results have indicated that τ α is related to the Debye–Waller factor 〈 u 2 〉, a measure of picosecond‐timescale segmental rattling, via a universal relationship predicted by the generalized localization model (GLM) of supercooled liquid dynamics . Unlike the CRRs underlying the AG theory, 〈 u 2 〉 is experimentally quantifiable via methods including incoherent neutron scattering, Mossbauer scattering, and time‐resolved Stokes‐shift experiments . As such, any theory elucidating the relationship between 〈 u 2 〉 and relaxation dynamics in ionomers would provide a particularly useful framework for ionomer understanding and design.…”

Stabilization of proteins in solid form

“…Recently it has been shown that a surrogate for <u 2 > from neutron scattering could be found in signatures of time-dependent fluorescence from a probe molecule located within the formulation of interest [92]. However, technical challenges prevented this method from being used for powder samples.…”

An Emerging Unified View of Dynamic Interphases in Polymers

“…The success of ⟨ u 2 ⟩ as a measure of the softness of confinement can be understood based upon a general scaling relationship between ⟨ u 2 ⟩, which is an experimentally accessible measure of local segmental rattle space on a picosecond timescale, and the high‐frequency shear modulus, . In essence, this result indicates that the dynamics of near‐interface polymers are more sensitive to interfacial energy when they are confined by a material exhibiting a relatively high glassy modulus.…”