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Full-Text Articles in Physics
Diffraction Of A Gaussian Beam By A Spherical Obstacle, James A. Lock, Edward A. Hovenac
Diffraction Of A Gaussian Beam By A Spherical Obstacle, James A. Lock, Edward A. Hovenac
Physics Faculty Publications
The Kirchhoff integral for diffraction in the near-forward direction is derived from the exact solution of the electromagnetic boundary value problem of a focused Gaussian laser beam incident on a spherical particle. The diffracted intensity in the vicinity of the particle is computed and the way in which the features of the diffraction pattern depend on the width of the Gaussian beam is commented on.
Thermally Activated Escape Over Fluctuating Barriers, Ulrich Zürcher, Charles R. Doering
Thermally Activated Escape Over Fluctuating Barriers, Ulrich Zürcher, Charles R. Doering
Physics Faculty Publications
We investigate the thermally activated escape of a Brownian particle over a potential barrier whose height fluctuates with a rate α between the values E+ and E−. We are mainly interested in the low-temperature behavior where E+/T≫E−/T. We calculate the mean exit time as a function of the rate of the barrier fluctuations for the piecewise linear and the piecewise constant barrier, τ=τ(α). For the piecewise constant potential we find three different regimes: τ∼τ+ for α<τ−1+=exp(-E+/T), τ∼2τ− for α>τ−1−=exp(-E−/T), and τ∼α−1 for τ−1+<α<τ−1−. The mean exit time for the piecewise linear potential has a different behavior for fast barrier fluctuations, α>τ−1−; τ(α) is a monotonously increasing function that approaches the asymptotic value τ∼ √τ+τ− for α→∞. We show that …
Contribution Of High-Order Rainbows To The Scattering Of A Gaussian Laser Beam By A Spherical Particle, James A. Lock
Contribution Of High-Order Rainbows To The Scattering Of A Gaussian Laser Beam By A Spherical Particle, James A. Lock
Physics Faculty Publications
I review the theory of the scattering of a Gaussian laser beam by a dielectric spherical particle and give the details for constructing a computer program to implement the theory. Computational results indicate that if the width of the laser beam is much less than the diameter of the particle and if the axis of the beam is incident near the edge of the particle, the fifth-, sixth-, and ninth-order rainbows should be evident in the far-field scattered intensity. I performed an experiment that yielded tentative evidence for the presence of the sixth-order rainbow.