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Rotational Brownian motion
About: Rotational Brownian motion is a research topic. Over the lifetime, 227 publications have been published within this topic receiving 7207 citations.
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TL;DR: The nuclear spin relaxation times T1 and T2 have been calculated for two identical nuclei of spin I = ½ fixed in an ellipsoid undergoing rotational Brownian motion as discussed by the authors.
Abstract: The nuclear spin relaxation times T1 and T2 have been calculated for two identical nuclei of spin I = ½ fixed in an ellipsoid undergoing rotational Brownian motion. The ellipsoid is subject to small random changes in orientation in which the rotation probabilities about its three major axes are different. This anisotropic motion yields five nuclear correlation times; isotropic motion yields only one correlation time. The results are applicable provided that the static dipolar coupling is effectively averaged to small values by the rotational motion. For nonviscous liquids, T1 = T2. When the rotation probabilities about two axes are equal, the relaxation‐time expressions simplify a great deal, but they retain the essential relaxation features of anisotropic rotational motion; the number of nuclear correlation times is reduced to three; the relaxation times for rapid motion have been calculated as a function of the ratio of the two rotation probabilities for this case. The relaxation rates in ellipsoids of ...
842 citations
01 Mar 2004
TL;DR: In this article, the problem of solving Langevin and Fokker-Planck Equations has been studied in the presence of an external potential with applications to Dielectric and Kerr Effect Relaxation in Fluids and Liquid Crystals.
Abstract: Historical Background and Introductory Concepts Methods for Solving Langevin and Fokker-Planck Equations Matrix Continued Fractions Escape Rate Theory Linear and Nonlinear Response Theory Brownian Motion of a Free Particle and a Harmonic Oscillator Rotational Brownian Motion about a Fixed Axis in a Periodic Potential Brownian Motion in a Tilted Periodic Potential: Application to the Josephson Tunnelling Junction and Ring Lasers Brownian Motion in a Double-Well Potential Isotropic and Anisotropic Rotational Brownian Motion in Space in the Presence of an External Potential with Applications to Dielectric and Kerr Effect Relaxation in Fluids and Liquid Crystals Brownian Motion of Classical Spins with Applications to Superparamagnetism Magnetic Stochastic Resonance Dynamic Hysteresis Switching Field Surfaces Inertial Langevin Equations with Applications to Orientational Relaxation in Liquids Itinerant Oscillator Model Anomalous Diffusion Continuous Time Random Walks Methods for the Solution of Fractional Fokker-Planck Equations.
548 citations
01 Jun 1974
TL;DR: In this paper, a theory connecting rotational brownian motion with intensity fluctuations of the light emitted from fluorescent molecules excited by linearly polarized light is given, which does not depend on the close relationship between fluorescence lifetime and rotational relaxation times, which makes an enlarged time range available for fluorescence spectroscopy.
Abstract: A theory, which connects rotational brownian motion with intensity fluctuations of the light emitted from fluorescent molecules excited by linearly polarized light, is given. Analysis of rotational diffusion in this way does not depend on the close relationship between fluorescence lifetime and rotational relaxation times, which is necessary in present methods and thus makes an enlarged time range available for fluorescence spectroscopy. When short fluorescence lifetimes are used the rotational diffusion of the molecule in its ground state will be observed.
392 citations
TL;DR: In this paper, the theory of dielectric relaxation in a model polar liquid is developed and applied to experimental data, where a permanent point dipole moment undergoes rotational Brownian motion in the cavity.
Abstract: The theory of dielectric relaxation in a model polar liquid is developed and applied to experimental data. The model is a spherical Onsager cavity, with a uniform dielectric background described by the high frequency limit e∞ and containing a permanent point dipole. The dipole moment undergoes rotational Brownian motion in the cavity. Dielectric friction on the rotating dipole is taken into account and leads to a frequency‐dependent relaxation time. Earlier theoretical results, obtained first by Klug, Kranbuehl, and Vaughn and by Fatuzzo and Mason, are rederived. When the rotational Brownian motion is spherically isotropic, approximate Debye relaxation is found. When the rotational Brownian motion of the dipole is restricted to a constant angle with respect to some fixed axis, approximate Davidson–Cole relaxation is found. Experimental data on glycerol and i‐amylbromide are analyzed this way.
387 citations
TL;DR: Simulations based on this model reproduce the density distributions measured for the small bacteria E. coli and Caulobacter crescentus, as well as for the much larger bull spermatozoa swimming between two walls.
Abstract: In this Letter we propose a kinematic model to explain how collisions with a surface and rotational Brownian motion give rise to accumulation of microswimmers near a surface. In this model, an elongated microswimmer invariably travels parallel to the surface after hitting it from an oblique angle. It then swims away from the surface, facilitated by rotational Brownian motion. Simulations based on this model reproduce the density distributions measured for the small bacteria E. coli and Caulobacter crescentus, as well as for the much larger bull spermatozoa swimming between two walls.
294 citations