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Title: Change of translational-rotational coupling in liquids revealed by field-cycling {sup 1}H NMR

Abstract

Applying the field-cycling nuclear magnetic resonance technique, the frequency dependence of the {sup 1}H spin-lattice relaxation rate, R{sub 1}(ω)=T{sub 1}{sup −1}(ω), is measured for propylene glycol (PG) which is increasingly diluted with deuterated chloroform. A frequency range of 10 kHz–20 MHz and a broad temperature interval from 220 to about 100 K are covered. The results are compared to those of experiments, where glycerol and o-terphenyl are diluted with their deuterated counter-part. Reflecting intra- as well as intermolecular relaxation, the dispersion curves R{sub 1}(ω,x) (x denotes mole fraction PG) allow to extract the rotational time constant τ{sub rot}(T, x) and the self-diffusion coefficient D(T, x) in a single experiment. The Stokes-Einstein-Debye (SED) relation is tested in terms of the quantity D(T, x) τ{sub rot}(T, x) which provides a measure of an effective hydrodynamic radius or equivalently of the spectral separation of the translational and the rotational relaxation contribution. In contrast to o-terphenyl, glycerol and PG show a spectral separation much larger than suggested by the SED relation. In the case of PG/chloroform mixtures, not only an acceleration of the PG dynamics is observed with increasing dilution but also the spectral separation of rotational and translational relaxation contributions continuously decreases. Finally,more » following a behavior similar to that of o-terphenyl already at about x = 0.6; i.e., while D(T, x) τ{sub rot}(T, x) in the mixture is essentially temperature independent, it strongly increases with x signaling thus a change of translational-rotational coupling. This directly reflects the dissolution of the hydrogen-bond network and thus a change of solution structure.« less

Authors:
; ;  [1]
  1. Experimentalphysik II, Universität Bayreuth, D-95440 Bayreuth (Germany)
Publication Date:
OSTI Identifier:
22416020
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 3; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CHLOROFORM; COUPLING; DILUTION; DISSOLUTION; FREQUENCY DEPENDENCE; GLYCEROL; GLYCOLS; HYDROGEN 1; KHZ RANGE; LIQUIDS; MHZ RANGE; NUCLEAR MAGNETIC RESONANCE; PROPYLENE; SELF-DIFFUSION; SPIN-LATTICE RELAXATION

Citation Formats

Meier, R., Schneider, E., and Rössler, E. A.. Change of translational-rotational coupling in liquids revealed by field-cycling {sup 1}H NMR. United States: N. p., 2015. Web. doi:10.1063/1.4904719.
Meier, R., Schneider, E., & Rössler, E. A.. Change of translational-rotational coupling in liquids revealed by field-cycling {sup 1}H NMR. United States. doi:10.1063/1.4904719.
Meier, R., Schneider, E., and Rössler, E. A.. Wed . "Change of translational-rotational coupling in liquids revealed by field-cycling {sup 1}H NMR". United States. doi:10.1063/1.4904719.
@article{osti_22416020,
title = {Change of translational-rotational coupling in liquids revealed by field-cycling {sup 1}H NMR},
author = {Meier, R. and Schneider, E. and Rössler, E. A.},
abstractNote = {Applying the field-cycling nuclear magnetic resonance technique, the frequency dependence of the {sup 1}H spin-lattice relaxation rate, R{sub 1}(ω)=T{sub 1}{sup −1}(ω), is measured for propylene glycol (PG) which is increasingly diluted with deuterated chloroform. A frequency range of 10 kHz–20 MHz and a broad temperature interval from 220 to about 100 K are covered. The results are compared to those of experiments, where glycerol and o-terphenyl are diluted with their deuterated counter-part. Reflecting intra- as well as intermolecular relaxation, the dispersion curves R{sub 1}(ω,x) (x denotes mole fraction PG) allow to extract the rotational time constant τ{sub rot}(T, x) and the self-diffusion coefficient D(T, x) in a single experiment. The Stokes-Einstein-Debye (SED) relation is tested in terms of the quantity D(T, x) τ{sub rot}(T, x) which provides a measure of an effective hydrodynamic radius or equivalently of the spectral separation of the translational and the rotational relaxation contribution. In contrast to o-terphenyl, glycerol and PG show a spectral separation much larger than suggested by the SED relation. In the case of PG/chloroform mixtures, not only an acceleration of the PG dynamics is observed with increasing dilution but also the spectral separation of rotational and translational relaxation contributions continuously decreases. Finally, following a behavior similar to that of o-terphenyl already at about x = 0.6; i.e., while D(T, x) τ{sub rot}(T, x) in the mixture is essentially temperature independent, it strongly increases with x signaling thus a change of translational-rotational coupling. This directly reflects the dissolution of the hydrogen-bond network and thus a change of solution structure.},
doi = {10.1063/1.4904719},
journal = {Journal of Chemical Physics},
number = 3,
volume = 142,
place = {United States},
year = {Wed Jan 21 00:00:00 EST 2015},
month = {Wed Jan 21 00:00:00 EST 2015}
}