Low-temperature relaxation of polymers around doped dyes studied by persistent spectral hole burning

Heterogeneous dynamics in liquids: fluctuations in space and time

“…Occasionally, these methods are referred to as 'hole burning' experiments, in analogy to the optical hole burning performed in low temperature glasses. Optical hole burning exploits the possibility of modifying an extremely narrow subset of transition frequencies (those which are in resonance with the laser frequency) out of the entire inhomogeneously broadened absorption spectrum of chromophores in a relatively rigid matrix [75][76][77]. These studies demonstrate clearly that the inhomogeneous broadening of optical lines originates from the previously anticipated heterogeneity regarding the local electric fields [78].…”

Local free volume and structural relaxation studied with photoisomerization of azobenzene and persistent spectral hole burning in poly(alkyl methacrylate)s at low temperatures

“…9 -11 Temperature dependence of the irreversible increase in hole width for amorphous polymer solids in PSHB temperature cycling experiments reflects sensitive thermally activated local structural relaxation of the matrices. 12,13 Local structural relaxation in amorphous glassy polymers has been studied with the measurements of dielectric relaxation, 14 mechanical relaxation, 15,16 NMR,17,18 and so on. The previous results of our PSHB temperature cycling experiments 13,19 in various poly(alkyl methacrylate)s above 20 K were consistent with those of dielectric and mechanical relaxation.…”

“…12,13 Local structural relaxation in amorphous glassy polymers has been studied with the measurements of dielectric relaxation, 14 mechanical relaxation, 15,16 NMR,17,18 and so on. The previous results of our PSHB temperature cycling experiments 13,19 in various poly(alkyl methacrylate)s above 20 K were consistent with those of dielectric and mechanical relaxation. In addition, the beginning of the local structural relaxation at low temperatures is sensitively detected by PSHB measurements, because the results of PSHB are obtained as the accumulated amounts of the relaxation processes in frequencies of very wide range.…”

Mechanical hole-burning spectroscopy: Demonstration of hole burning in the terminal relaxation regime

“…[3][4][5][6][7][8][9][10] While it is widely accepted that the dynamics can be represented by a broad distribution of relaxation times or other nonexponential decay function, such as the Kolrausch-Williams-Watts ͑KWW͒ 11,12 stretched exponential, it is less clear whether this dispersion exhibits a uniform relaxation mechanism ͑homogeneous͒, or the net broadened relaxation is heterogeneous due to the response of slow and fast subensembles with independent mechanisms, which might be spatially distributed in the material. 3,[13][14][15] There has been a range of techniques used to test the heterogeneity of the relaxational dynamics, such as multidimensional nuclear magnetic resonance, 16 optical deep bleaching, 17 nonresonant spectral hole burning ͑NSHB͒ conducted in dielectric and magnetic fields, 5,14,15,[18][19][20][21][22] and recently, mechanical spectral hole burning ͑MSHB͒. 10 The fundamental assumption behind these spectral hole-burning techniques is that the spectrum of relaxation times can be locally altered rather than uniformly shifted by a strong impulse of given frequency.…”