# Measurement of the Instantaneous Velocity of a Brownian Particle

@article{Li2010MeasurementOT, title={Measurement of the Instantaneous Velocity of a Brownian Particle}, author={Tongcang Li and Simon Kheifets and David Medellin and Mark Raizen}, journal={Science}, year={2010}, volume={328}, pages={1673 - 1675} }

Dancing in the Light Nearly 200 years ago, the botanist Robert Brown noted that pollen particles floating on a liquid displayed a random motion, jittering under the microscope as if the particles were alive. In 1905, Albert Einstein described this Brownian motion in terms of statistical thermodynamics. Now, Li et al. (p. 1673, published online 20 May) use a single, optically trapped silica bead to probe the dynamics of Brownian motion, measuring the predicted instantaneous velocity of the…

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## References

SHOWING 1-10 OF 26 REFERENCES

Direct observation of nondiffusive motion of a Brownian particle.

- PhysicsPhysical review letters
- 2005

It is found that the transition from ballistic to diffusive motion is delayed to significantly longer times than predicted by the standard Langevin equation, a consequence of the inertia of the fluid.

Measurement of the translational and rotational Brownian motion of individual particles in a rarefied gas.

- PhysicsPhysical review letters
- 2006

It is found that the translational and rotational diffusion can be described by the relation given by Uhlenbeck and Ornstein and can be used for the determination of the moments of inertia of small particles.

Brownian Motion of an Ellipsoid

- PhysicsScience
- 2006

The Brownian motion of isolated ellipsoidal particles in water confined to two dimensions is studied and the effects of coupling between rotational and translational motion are elucidated by using digital video microscopy and Langevin theory and numerical simulations.

Brownian Motion and Nonequilibrium Statistical Mechanics

- PhysicsScience
- 1986

The fluctuation-dissipation theorem, which states that irreversible processes ip nonequilibrium are necessarily related to thermal fluctuations in equilibrium, is described and the meaning of stochastization is considered.

Toward quantum superposition of living organisms

- Physics
- 2010

The most striking feature of quantum mechanics is the existence of superposition states, where an object appears to be in different situations at the same time. The existence of such states has been…

Experimental demonstration of violations of the second law of thermodynamics for small systems and short time scales.

- PhysicsPhysical review letters
- 2002

The fluctuation theorem is experimentally demonstrated by following the trajectory of a colloidal particle captured in an optical trap that is translated relative to surrounding water molecules to show entropy consumption can occur over colloidal length and time scales.

Compressibility effects in the hydrodynamic theory of Brownian motion

- Physics, MathematicsJournal of Fluid Mechanics
- 1975

The velocity correlation function of a Brownian particle in a viscous compressible fluid is studied in the limit of very small compressibility. The main effect of compressibility is an initial rapid…

Cavity opto-mechanics using an optically levitated nanosphere

- PhysicsProceedings of the National Academy of Sciences
- 2009

A novel approach is proposed, in which optically levitating a nano-mechanical system can greatly reduce its thermal contact, while simultaneously eliminating dissipation arising from clamping, which potentially opens the door to ground-state cooling and coherent manipulation of a single mesoscopic mechanical system or entanglement generation between spatially separate systems, even in room-temperature environments.

Sub-kelvin optical cooling of a micromechanical resonator

- PhysicsNature
- 2006

Active optical feedback cooling to 135 ± 15 mK of a micromechanical resonator integrated with a high-quality optical resonator is demonstrated, allowing cooling to near the ground state that is required for quantum experiments—near 100 nK for a kHz oscillator.