Purely mechanical solvation dynamics in supercooled liquids: The S0 ← T1 (0-0) transition of naphthalene

Hauke Wendt, Ranko Richert

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Abstract

We have measured the Stokes shift and its dynamics for the probe molecules naphthalene (Δμ ≈ 0) and quinoxaline (Δμ ≈ 1.3 D) in n-propanol and other glass-forming solvents. The Stokes shift for naphthalene (≈63 cm-1) turns out to be independent of the solvent polarity over a wide range of the static dielectric constants. Its time dependence is governed by the structural (or α- or shear stress) relaxation time of n-propanol, without any signature of the strong dielectric relaxation. For this solvent, structural and dipolar contributions can be distinguished because the time scale for dipole reorientation is a factor of 25 slower than the α-relaxation time. We conclude that the solvation of naphthalene reflects excitation-induced changes in the van der Waals interactions, which makes it an ideal probe for assessing shear stress or mechanical relaxations on microscopic spatial scales near Tg.

Original languageEnglish (US)
Pages (from-to)5775-5781
Number of pages7
JournalJournal of Physical Chemistry A
Volume102
Issue number29
StatePublished - Jul 16 1998
Externally publishedYes

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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