Probing organic glasses at low temperature with variable time scale optical dephasing measurements

Narasimhan, L. R.; Littau, Karl A.; Pack, Dee William; Bai, Yanling; Elschner, Andreas; Fayer, M. D.

doi:10.1021/cr00101a001

Cited by 225 publications

(154 citation statements)

References 44 publications

(59 reference statements)

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“…The fast process always occurred on a time scale faster than their time resolution, but the rate of the slow process could be altered by changing the temperature. A variety of relaxation time scales in this experiment, performed just below the glass transition temperature, is consistent with extensive optical nonlinear experimental studies of chromophores in low temperature ethanol glass [2]. However, long-lived inhomogeneous broadening in the liquid phase has not been addressed in detail.…”

Section: Introductionsupporting

confidence: 79%

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Nanosecond timescale optical inhomogeneous broadening of dye molecules in liquids at and near room temperature

Stein

Fayer

1991

Chemical Physics Letters

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Time-resolved fluorescence depolarization measurements of the S& electronic absorption band of rhodamine B in glycerol and propylene glycol have been made at different excitation wavelengths. It was found that electronic excitation transport between the rhodamine B chromophores is dispersive in glycerol at room temperature and in propylene glycol below 250 K. This demonstrates inhomogeneous broadening of the dye absorption spectrum which persists for the time scale of the fluorescence lifetime (nanoseconds) or longer. Measurements of time-resolved emission spectra at a number of different excitation wavelengths and temperatures support this conclusion and suggest that the chromophore-solvent microenvironments causing inhomogeneous broadening are the same as those responsible for the dynamic Stokes shift about an excited chromophore.

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Section: Introductionsupporting

confidence: 79%

“…The concepts of dynamical (homogeneous and spectral diffusion) broadening and inhomogenous broadening of an optical transition of a solute have been closely examined in recent years [ 1,2]. It is now accepted that there are many time scales governing solute-solvent interactions.…”

Section: Introductionmentioning

confidence: 99%

Nanosecond timescale optical inhomogeneous broadening of dye molecules in liquids at and near room temperature

Stein

Fayer

1991

Chemical Physics Letters

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“…The observed T 1.3 temperature dependence seems to point to more or less conventional glass dynamics. However, it should be mentioned that the dephasing times of isolated systems, embedded in amorphous hosts, are usually 2 orders of magnitude longer 56,57 than the times found in this paper for both LH2 and LH1. Evidently, the strong and specific chromophore-protein coupling determines T 2 * to a large extent, and causes modulation of the transition frequency even at temperatures as low as a few Kelvin.…”

Section: Discussioncontrasting

confidence: 61%

Exciton Dynamics in LH1 and LH2 of Rhodopseudomonas Acidophila and Rhodobium Marinum Probed with Accumulated Photon Echo and Pump−Probe Measurements

et al. 2000

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Exciton dynamics in the B850 and B875 bands of isolated complexes of Rhodopseudomonas acidophila (strain 10 050 and 7050) and in the B875 band of isolated complexes of Rhodobium marinum were investigated by means of accumulated photon echo and pump-probe techniques at different temperatures and wavelengths. For all three systems, the optical dephasing time T 2 was found to be very similar: at 4.2 K, T 2 is 116 and 106 ps for the B850 and B875 bands of Rhodopseudomonas acidophila, respectively, and 93 ps for the B875 band of Rhodobium marinum. The rapid dephasing, which displays glassy character, is a consequence of the strong pigment-protein interactions that arise through the rather short distances in these complexes. The observed dephasing time at the red edge of the B850 band of Rhodopseudomonas acidophila at 4.2 K reveals the existence of spectral diffusion in this system. From the wavelength dependence of the pump-probe signal in the B875 LH1 band of Rhodopseudomonas acidophila at 3 K it is concluded that energy transfer between energetically inequivalent LH1 rings occurs on a time scale of several tens picoseconds, while energy trapping takes place in about 250 ps.

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“…34 Aging effects, demonstrating this non-equilibrium evolution, have been observed with, for example, burning hole experiments in organic glasses (see Ref. [35] and references therein). In the context of magnetic disordered systems with explicit quenched disorder like LiHo x Y 1−x F 4 , a great effort has been devoted to the study of the quantum phase transition and the dynamics close to the quantum critical point.…”

Section: Discussionmentioning

confidence: 81%

“…It is then plausible that even at very low temperatures, say T = 0, with only quantum fluctuations driving the dynamics, the materials and/or models will need an unaffordable long time to reach equilibrium and that the relevant evolution will be characterized by non-equilibrium effects. Indeed, it is well-known that certain glasses in the limit of very low temperatures have aging effects 34,35 and hence the approaches based on the assumption of equilibration have a restricted domain of application. Instead, one should necessarily start from a quantum dynamic description in order to obtain sensible information about the systems.…”

Section: Introductionmentioning

confidence: 99%

Real-time nonequilibrium dynamics of quantum glassy systems

1999

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We develop a systematic analytic approach to aging effects in quantum disordered systems in contact with an environment. Within the closed-time path-integral formalism we include dissipation by coupling the system to a set of independent harmonic oscillators that mimic a quantum thermal bath. After integrating over the bath variables and averaging over disorder we obtain an effective action that determines the real-time dynamics of the system. The classical limit yields the Martin-Siggia-Rose generating functional associated to a colored noise. We apply this general formalism to a prototype model related to the p spin-glass. We show that the model has a dynamic phase transition separating the paramagnetic from the spin-glass phase and that quantum fluctuations depress the transition temperature until a quantum critical point is reached. We show that the dynamics in the paramagnetic phase is stationary but presents an interesting crossover from a region controlled by the classical critical point to another one controlled by the quantum critical point. The most characteristic property of the dynamics in a glassy phase, namely aging, survives the quantum fluctuations. In the sub-critical region the quantum fluctuation-dissipation theorem is modified in a way that is consistent with the notion of effective temperatures introduced for the classical case. We discuss these results in connection with recent experiments in dipolar quantum spin-glasses and the relevance of the effective temperatures with respect to the understanding of the low temperature dynamics.

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Probing organic glasses at low temperature with variable time scale optical dephasing measurements

Cited by 225 publications

References 44 publications

Nanosecond timescale optical inhomogeneous broadening of dye molecules in liquids at and near room temperature

Nanosecond timescale optical inhomogeneous broadening of dye molecules in liquids at and near room temperature

Exciton Dynamics in LH1 and LH2 of Rhodopseudomonas Acidophila and Rhodobium Marinum Probed with Accumulated Photon Echo and Pump−Probe Measurements

Real-time nonequilibrium dynamics of quantum glassy systems

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