Observation of fast time scale spectral diffusion in a low temperature glass: comparison of picosecond photon and stimulated echoes

Narasimhan, L. R.; Bai, Yu; Dugan, Mark; Fayer, M. D.

doi:10.1016/0009-2614(91)90040-g

Cited by 43 publications

(24 citation statements)

References 24 publications

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“…93, 95,102 In order to resolve this discrepancy, one phenomenologically introduces an ad hoc distribution of A that goes such as A µ , with µ a small fraction, typically around 0.3. 15,95,96,[124][125][126][127][128][129][130] This yields hole widths whose temperature dependence is dominated by a T 1+µ power law, in accord with experiment. Although the behavior of this distribution function at A f 0, where it goes to zero, is surely unrealistic, the main effect of this modification is to make the distribution rise slowly, rather than being a constant throughout most of the range of values of A.…”

Section: Two-level System and Sudden Jump Modelssupporting

confidence: 61%

Theory of Single-Molecule Optical Line-Shape Distributions in Low-Temperature Glasses

1997

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We present a theoretical framework for analyzing the distribution of optical line shapes in low-temperature glasses, as measured by single-molecule spectroscopy. The theory is based on the standard tunneling twolevel system model of low-temperature glasses and on the stochastic sudden jump model for the two-level system dynamics. Within this framework we present an explicit formula for the line shape of a single molecule and employ Monte Carlo simulation techniques to calculate the distribution of single-molecule line shapes. We compare our calculated line-width distributions to those measured experimentally. We find that the twolevel system model captures the features of the experimental line-width distributions very well, although there are discrepancies for small line widths. We also discuss the relation of single-molecule line-shape distributions to more traditional "line shapes", as measured by hole-burning and photon echo spectroscopies. Using the results from our analysis of the single-molecule line-width distributions, with no adjustable parameters we can compare theoretical predictions with experiment for photon echo decay times and hole widths. In general, the agreement is good, providing further evidence that the standard tunneling model in glasses is basically correct. For two systems, however, theory and experiment do not agree quantitatively.

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Section: Two-level System and Sudden Jump Modelssupporting

confidence: 61%

Theory of Single-Molecule Optical Line-Shape Distributions in Low-Temperature Glasses

1997

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“…͑2.5͒ when ϷT w cannot be done analytically 34 and must be evaluated numerically. However, when T w ӷ, Eq.…”

Section: A General Formulationmentioning

confidence: 99%

Electronic spectral diffusion in glasses: The influence of coupling to the medium on experimental observables

Zimdars

Fayer

1996

The Journal of Chemical Physics

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The theory of electronic dephasing in low temperature glasses is extended to include the possibility that the strength of coupling of the chromophore to the solvent medium depends on the nature of the bath dynamical processes and the nature of the chromophore and, therefore, the chromophore-bath coupling can vary as a function of the rate of the dynamics of the medium. In the context of the sudden jump two-level system ͑TLS͒ model of low temperature glasses, this theory is used to reconcile the apparent contradiction implied by differences observed in spectral diffusion data for cresyl violet and metal-porphyrins in deuterated ethanol glass at 1.5 K. Previously, the coupling strength of a chromophore to the TLS has been assumed to be independent of rate of the transition between TLS states. Within the context of this approximation, spectral diffusion data yield, P i (R), the intrinsic TLS fluctuation rate distribution. With the inclusion of the rate dependent coupling, C(R), it is shown that the spectral diffusion observables actually yield P i (R)C(R). Therefore, the observed lack of spectral diffusion for a particular chromophore over some range of times can imply C(R) is zero rather than the current interpretation that P i (R) is zero. To illustrate the importance of C(R), a hueristic model is analyzed. A fluctuation rate distribution is introduced that consists of the sum of three log-normal functions each associated with a specific class of dynamics occurring over three overlapping ranges of rates. The uncharged and nonpolar metal porphyrins is taken to couple to TLS strain dipoles, while the charged and polar cresyl violet also couples to TLS electric dipoles. By taking one of the types of TLS dynamics to only give rise to electric dipole fluctuations, it is possible to fit all of the experimental data in deuterated ethanol with a single intrinsic distribution of TLS fluctuation rates. This analysis of previously reported data is supported by the presentation of new stimulated photon echo data on both cresyl violet and zinc meso-tetraphenyl porphine in deuterated ethanol.

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“…7,8 On approaching the glass transition, the large-scale motion becomes more and more impeded by the increasing structural constraints. [9][10][11][12] Molecules, or subunits of macromolecules, are surrounded and trapped by rigid pockets, which are usually referred to as cages.…”

Section: Introductionmentioning

confidence: 99%

“…33 Notably, primary and stimulated echoes were jointly analyzed before to investigate the optical dephasing of dyes due to the structural relaxation of the glassy host. 7,8 As a model system to study cage motion over a wide range of time scales we employ ionic spin probes that are immobilized on the surface of ionic clusters in ionomers due to electrostatic attachment. 37,38 Such attachment was found to prevent wide-angle reorientation of the probes up to temperatures that are 100 K higher than the glass transition temperature.…”

Section: Introductionmentioning

confidence: 99%

Electron spin relaxation due to small-angle motion: Theory for the canonical orientations and application to hierarchic cage dynamics in ionomers

Leporini

Schädler

Wiesner

et al. 2003

The Journal of Chemical Physics

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Analytical expressions for transverse electron spin relaxation induced by small angle motion were derived for the first time within an anisotropic model for rotational diffusion by using an approximation of the spin Hamiltonian and its variation during reorientation that is valid close to the canonical orientations. The dependence of the decay of the stimulated echo on such motion was studied by extensive Monte Carlo simulations and regimes were identified in which the time constant of this decay is related to parameters of the anisotropic diffusion model by simple equations. For testing these theoretical findings and obtaining insight into hierarchical cage dynamics in soft matter, high-field electron paramagnetic resonance (EPR) measurements were performed at a frequency of 94 GHz where the canonical orientations for nitroxide spin labels are well resolved. A combination of continuous wave EPR, saturation recovery measurements, and measurements of the decay of primary and stimulated electron spin echoes was employed to cover time scales from a few picoseconds up to several microseconds. Ionic spin probes attached by electrostatic interactions to the surface of ionic clusters in ionomers were used as a model system in which slow cage reorientation can be studied in the glass transition region of the polymer (0.64

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Observation of fast time scale spectral diffusion in a low temperature glass: comparison of picosecond photon and stimulated echoes

Cited by 43 publications

References 24 publications

Theory of Single-Molecule Optical Line-Shape Distributions in Low-Temperature Glasses

Theory of Single-Molecule Optical Line-Shape Distributions in Low-Temperature Glasses

Electronic spectral diffusion in glasses: The influence of coupling to the medium on experimental observables

Electron spin relaxation due to small-angle motion: Theory for the canonical orientations and application to hierarchic cage dynamics in ionomers

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