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Full-Text Articles in Physics
Relativistic Corrections To A Generalized Sum Rule, P.T. Leung, H. Sinky
Relativistic Corrections To A Generalized Sum Rule, P.T. Leung, H. Sinky
Physics Faculty Publications and Presentations
Relativistic corrections to a previously established generalized sum rule are obtained using the Foldy-Wouthysen transformation. This sum rule derived previously by Wang [Phys. Rev. A 60, 262 (1999)] for a nonrelativistic system contains both the well-known Thomas-Reiche-Kuhn and Bethe sum rules, for which relativistic corrections have been obtained in the literature. Our results for the generalized formula will be applied to recover several results obtained previously in the literature, as well as to another sum rule whose relativistic corrections will be obtained.
Existence Of The Dielectric Constant In Fluids Of Classical Deformable Molecules, John D. Ramshaw
Existence Of The Dielectric Constant In Fluids Of Classical Deformable Molecules, John D. Ramshaw
Physics Faculty Publications and Presentations
The existence of the dielectric constant epsilon is investigated for fluids composed of classical deformable (polarizable) molecules. The development is based upon generalized functional-derivative relations which involve joint distributions in molecular positions r/sub k/ and dipole moments ..mu../sub k/. Sufficient conditions for the existence of epsilon are expressed in terms of the generalized direct correlation function c(12) = c(r/sub 1/, ..mu../sub 1/; r/sub 2/, ..mu../sub 2/). It is found that epsilon exists if -kTc(12) depends only on relative positions and dipole moment directions (in addition to Vertical Bar..mu../sub 1/Vertical Bar and Vertical Bar..mu../sub 2/Vertical Bar), and becomes asymptotic to the …
Time-Dependent Direct Correlation Function, John D. Ramshaw
Time-Dependent Direct Correlation Function, John D. Ramshaw
Physics Faculty Publications and Presentations
A time-dependent direct correlation function (TDDCF) is defined and discussed. The definition (which differs from that proposed by Percus and Yevick) is motivated by linear response theory. The TDDCF consequently has a functional-derivative or stimulus-response interpretation closely analogous to that of the static direct correlation function. Mean-field considerations suggest that the TDDCF separates into a term which is simply related to the pair potential and a spatially shorter-ranged remainder. This behavior is confirmed in the Vlasov-Zwanzig approximation.
Decay Of Multiple Spin Echoes In Dipolar Solids, C. H. Wang, John D. Ramshaw
Decay Of Multiple Spin Echoes In Dipolar Solids, C. H. Wang, John D. Ramshaw
Physics Faculty Publications and Presentations
In this paper we derive a general expression describing the evolution of the transverse nuclear-spin magnetization for the Ostroff-Waugh multiple-spin-echo experiment in dipolar solids. Our approach consists of expressing the formula for the magnetization at even echoes in a form resembling an ordinary time-correlation function, and then evaluating this quantity by means of Zwanzig's projection-operator technique. For long times, we show that under certain conditions the echo envelope decays exponentially, in agreement with experiment. A general expression is obtained for the time constant T* associated with the decay. This result may be used to generate an expansion of 1T …