0000000000822532
AUTHOR
Ralph V. Chamberlin
Nonresonant Spectral Hole Burning in the Slow Dielectric Response of Supercooled Liquids
Large-amplitude, low-frequency electric fields can be used to burn spectral holes in the dielectric response of supercooled propylene carbonate and glycerol. This ability to selectively modify the dielectric response establishes that the non-Debye behavior results from a distribution of relaxation times. Refilling of the spectral hole was consistent with a single recovery time that coincided with the peak in the distribution. Moreover, refilling occurred without significant broadening, which indicates negligible direct exchange between the degrees of freedom that responded to the field. Nonresonant spectral hole burning facilitates direct investigation of the intrinsic response of systems t…
Slow Dielectric Relaxation of Supercooled Liqutos Investigated by Nonresonant Spectral Hole Burning
ABSTRACTWhen supercooled propylene carbonate and glycerol are subjected to a large-amplitude, low-frequency electric field, a spectral hole develops in their dielectric relaxation that is significantly narrower than their bulk response. This observation of nonresonant spectral hole burning establishes that the non-Debye response is due to a distribution of relaxation times. Refilling of the spectral hole occurs abruptly, indicative of a single recovery rate that corresponds to the peak in the distribution. The general shape of the spectral hole is preserved during recovery, indicating negligible interaction between the degrees of freedom that responded to the field. All relevant features in…
Nature of the non-exponential primary relaxation in structural glass-formers probed by dynamically selective experiments
Several experimental methods feature the potential to distinguish between slow and fast contributions to the non-exponential, ensemble averaged primary response in glass-forming materials. Some of these techniques are based on the selection of subensembles using multi-dimensional nuclear magnetic resonance, optical bleaching, and non-resonant spectral hole burning. Others, such as the time-dependent solvation spectroscopy, measure microscopic responses induced by local perturbations. Using several of these methods it could be demonstrated for various glass-forming materials that the non-exponential relaxation results from a superposition of dynamically distinguishable entities. The experime…
Dielectric study of supercooled triphenylphosphite and butyronitrile: Comparison with a mesoscopic model
Abstract Dielectric relaxation has been studied in the supercooled liquids triphenylphosphite (TPP) and butyrontrile (BN). BN is relatively strong according to Angell's classification and can be characterized by a fragility index m = 47. TPP, on the other hand, appears to be the most fragile non-polymeric liquid studied so far (m = 160). The dielectric response of the two glass-formers exhibits different degrees of non-exponentiality which is analyzed in terms of a mesoscopic model of dynamically correlated domains. The relation of this model to the strong versus fragile liquid classification scheme is discussed.
Nonresonant dielectric hole burning spectroscopy of supercooled liquids
The nonexponential response of propylene carbonate and glycerol near their glass transitions could be selectively altered using nonresonant spectral hole burning (NSHB) experiments. This observation provides evidence of the existence of a distribution of relaxation times in these supercooled liquids. NSHB is based on a pump, wait, and probe scheme and uses low-frequency large amplitude electrical fields to modify the dielectric relaxation. The temporal evolution of the polarization of the sample is then measured subsequent to a small voltage step. By variation of a recovery time inserted between pump and probe, the refilling of the spectral features could be monitored and was found to take …