From microscopic fluctuations to susceptibility spectra: single-molecule relaxation in glassy media

Siyang Wang; Jaladhar Mahato; Laura J. Kaufman

From microscopic fluctuations to susceptibility spectra: single-molecule relaxation in glassy media

Soft Condensed Matter 2026-07-02 v1

Authors: Siyang Wang , Jaladhar Mahato , Laura J. Kaufman

Abstract

Single-molecule (SM) rotational dynamics of fluorescent probes in polystyrene near the glass transition temperature ( $T_g$ ) are investigated over long times to reconstruct susceptibility spectra. The loss spectrum, commonly recorded using external field-driven (frequency-domain) spectroscopy, such as dielectric spectroscopy, is reconstructed from purely thermal SM rotational fluctuations. The results reproduce time-temperature superposition typically seen in dielectric spectroscopy for materials near $T_g$ and show that the ensemble spectrum is comprised of individual molecular responses to distinct environments.

Keywords

single-molecule dynamics glass transition susceptibility spectra rotational relaxation polystyrene time-temperature superposition

Cite

@article{arxiv.2607.02248,
  title  = {From microscopic fluctuations to susceptibility spectra: single-molecule relaxation in glassy media},
  author = {Siyang Wang and Jaladhar Mahato and Laura J. Kaufman},
  journal= {arXiv preprint arXiv:2607.02248},
  year   = {2026}
}