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A Surrogate for Debye-Waller Factors from Dynamic Stokes Shifts
Marcus T Cicerone1, Qin Zhong, Jerainne Johnson
1National Institute of Standards and Technology, Gaithersburg, MD 20899-8543.
The Journal of Physical Chemistry Letters
|June 25, 2011
Summary
Time-resolved fluorescence Stokes shifts (TRSS) mimic neutron scattering data, enabling Debye-Waller (DW) factor extraction. Caution is advised for DW factors ≥ 40 ps due to alpha relaxation influence in glassforming systems.
Area of Science:
- Physical Chemistry
- Materials Science
- Condensed Matter Physics
Background:
- Time-resolved fluorescence Stokes shifts (TRSS) and neutron scattering probe molecular dynamics.
- Understanding dynamics in glassforming systems requires accurate characterization of relaxation processes.
Purpose of the Study:
- To establish a correlation between TRSS and neutron scattering intermediate scattering functions.
- To develop a method for extracting Debye-Waller (DW) factor analogs from TRSS data.
- To investigate the influence of alpha relaxation on DW factors in glassforming systems.
Main Methods:
- Comparing short-time TRSS behavior with neutron scattering data near the static structure factor peak.
- Extracting a DW factor analog from TRSS data at picosecond timescales.
- Analyzing time-domain relaxation data to assess DW factor behavior.
Main Results:
- TRSS short-time dynamics closely resemble intermediate scattering functions from neutron scattering for glycerol.
- A DW factor analog can be reliably extracted from TRSS data as early as 1 ps.
- DW factors evaluated at times ≥ 40 ps are significantly influenced by alpha relaxation.
Conclusions:
- TRSS provides a viable alternative to neutron scattering for probing short-time dynamics and extracting DW factors.
- The influence of alpha relaxation on DW factors necessitates careful interpretation of dynamics in glassforming materials.
- This method offers a simplified approach to studying fast and slow dynamics in complex systems.
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