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Full-Text Articles in Physics
Failure Of The Optical Theorem For Gaussian-Beam Scattering By A Spherical Particle, James A. Lock, Joseph T. Hodges, Gérard Gouesbet
Failure Of The Optical Theorem For Gaussian-Beam Scattering By A Spherical Particle, James A. Lock, Joseph T. Hodges, Gérard Gouesbet
Physics Faculty Publications
It is shown that when an electromagnetic wave with some degree of amplitude rolloff in the transverse direction is scattered by a spherical particle, the optical theorem is not valid. For such shaped beams the extinction cross section may be written as an infinite series in powers of the reciprocal of the beam width. The imaginary part of the forward-scattering amplitude is shown to be the first term in this series. Two approximations to based on the dominance of diffraction in the forward direction for w(0) greater than or similar to a, where w(0) is the beam half-width and a …
A Stochastic Theory Of Inhomogeneously Broadened Linewidths In Solids, Ulrich Zürcher
A Stochastic Theory Of Inhomogeneously Broadened Linewidths In Solids, Ulrich Zürcher
Physics Faculty Publications
We investigate spectral diffusion decay using a model for solids that consists of two-level-systems (TLSs) interacting via strain fields. For the case when the rate of TLS flips vanishes, we find algebraic decay of correlation functions of the local field. We show that properties of equilibrium fluctuations are in agreement with the hierarchical picture proposed by Basché and Moerner: TLSs far away produce fast fluctuations that are small in magnitude, and close TLSs produce large fluctuations that are less frequent.
Interpretation Of Extinction In Gaussian-Beam Scattering, James A. Lock
Interpretation Of Extinction In Gaussian-Beam Scattering, James A. Lock
Physics Faculty Publications
The extinction efficiency for the interaction of a plane wave with a large nonabsorbing spherical particle is approximately 2.0. When a Gaussian beam of half-width w(0) is incident upon a spherical particle of radius a with w(o)/a < 1, the extinction efficiency attains unexpectedly high or low values, contrary to intuitive expectations. The reason for this is associated with the so-called compensating term in the scattered field, which cancels the field of the Gaussian beam behind the particle, thereby producing the particle's shadow. I introduce a decomposition of the total exterior field into incoming and outgoing portions that are free of compensating terms. It is then shown that a suitably defined interaction efficiency has the intuitively expected asymptotic values of 2.0 for w(o)/a >> 1 and 1.0 for w(o)/a << 1.
Partial-Wave Representations Of Laser Beams For Use In Light-Scattering Calculations, Gérard Gouesbet, James A. Lock, Gérard Gréhan
Partial-Wave Representations Of Laser Beams For Use In Light-Scattering Calculations, Gérard Gouesbet, James A. Lock, Gérard Gréhan
Physics Faculty Publications
In the framework of generalized Lorenz-Mie theory, laser beams are described by sets of beam-shape coefficients. The modified localized approximation to evaluate these coefficients for a focused Gaussian beam is presented. A new description of Gaussian beams, called standard beams, is introduced. A comparison is made between the values of the beam-shape coefficients in the framework of the localized approximation and the beam-shape coefficients of standard beams. This comparison leads to new insights concerning the electromagnetic description of laser beams. The relevance of our discussion is enhanced by a demonstration that the localized approximation provides a very satisfactory description of …
Is Fundamentals Of Physics Too Violent?: Reply, Victorial Kaspi, Jearl D. Walker
Is Fundamentals Of Physics Too Violent?: Reply, Victorial Kaspi, Jearl D. Walker
Physics Faculty Publications
No abstract provided.
Improved Gaussian Beam-Scattering Algorithm, James A. Lock
Improved Gaussian Beam-Scattering Algorithm, James A. Lock
Physics Faculty Publications
The localized model of the beam-shape coefficients for Gaussian beam-scattering theory by a spherical particle provides a great simplification in the numerical implementation of the theory. We derive an alternative form for the localized coefficients that is more convenient for computer computations and that provides physical insight into the details of the scattering process. We construct a FORTRAN program for Gaussian beam scattering with the localized model and compare its computer run time on a personal computer with that of a traditional Mie scattering program and with three other published methods for computing Gaussian beam scattering. We show that the …
A Thermodynamic Model For Pressurized Solids, Miron Kaufman, Herbert Schlosser
A Thermodynamic Model For Pressurized Solids, Miron Kaufman, Herbert Schlosser
Miron Kaufman
A thermodynamic model for solids under pressure is developed by assuming the universal equation of state and that under zero pressure the free energy is equal to the harmonic crystal (Debye) free energy. The model is applied to gold. In the case of nanocrystals this model reproduces the observed enhancement of the isobaric heat capacity and of the thermal expansion. Our model calculations are free of the ambiguities and inconsistencies connected with the Gruneisen equation, which was used in previous theoretical work.