Translational and rotational diffusion in supercooled orthoterphenyl close to the glass transition |
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Authors: | F Fujara B Geil H Sillescu G Fleischer |
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Institution: | (1) Institut für Physikalische Chemie, Universität Mainz, Jakob-Welder-Weg 15, W-6500 Mainz, Federal Republic of Germany;(2) Sektion Physik, Universität Leipzig, Linnéstrasse 5, O-7066 Leipzig, Federal Republic of Germany |
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Abstract: | Self diffusion coefficients in supercooled orthoterphenyl (OTP) have been determined down toD
t
=3·10–14 m2s–1 using a1H-NMR technique applying static field gradients up to 53T m–1 In a range of more than two decades theD
t
values agree with those of photochromic tracer molecules of the same size determined by forced Rayleigh scattering down to the glass transition temperatureT
g
. A change of mechanism is found for translational diffusion atT
c
1.2T
g
whereD
t
is proportional to the inverse shear viscosity
–1 atT>T
c
butD
t
![sim](/content/r9w81145w1515456/xxlarge8764.gif)
with =0.75 atT<T
c
. Rotational correlation times determined by2H-NMR stimulated echo techniques in deuterated OTP remain proportinal to
–1 down toT
g
. Our results are discussed in relation with mode coupling theory and with models of cooperative motion at the glass transition. |
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Keywords: | |
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