Effective masses of electrons, heavy holes and positrons in quasi-binary (GaSb)1−x(InAs)x crystals

The present investigation is focused on the effective masses of electrons, heavy holes and positrons in quasi-binary (GaSb)_1−x(InAs)_x crystals. To the best of our knowledge, this is the first time such quantities have been obtained for such a quasi-binary crystals. Our computations are based on the pseudopotential scheme within the virtual crystal approximation in which the effects of composition disorder are involved, while the positron wave function is evaluated under the point core approximation for the ionic potential. Comparisons are made with the measured values, which are only available for binary parent compounds and showed roughly good agreement. The calculated quantities in the quasi-binary crystals of interest are found to be generally different from those of the conventional quaternary alloys GaInAsSb which may provide more diverse opportunities to describe most carrier transport properties.     

Iodine hyperfine structure and absolute frequency measurements at 565, 576, and 585 nm

The hyperfine structure splittings of the P(10)14-1, R(15)14-1, and R(99)15-1 transitions at 585 nm, P(62)17-1 at 576 nm, and P(80)21-1 at 565 nm in ¹²⁷I₂ are measured by heterodyne spectroscopy using two dye lasers. In addition, the absolute frequencies of the hyperfine components P(10)14-1 a₁₅ and P(80)21-1 a₁₀ are determined using a self-referenced frequency comb. These frequencies are used in an experiment testing relativistic time dilation by laser spectroscopy on a fast ion beam.     

Hydrodynamic vector potentials

Solving the Navier-Stokes equation for incompressible fluids is greatly simplified by the solution of the vorticity equation. To accomplish this for three-dimensional flows requires vector potentials. These potentials are not only useful to take care of the incompressibility. Their modes are suitable also as test functions since the familiar Galerkin procedure does not work. The new method is checked by examples with known results and its relation to the classical approach with the stream function is clarified. The principle demonstration, however, concerns the transition to turbulence in plane shear flows. A simple layer of long rolls with axes parallel to the basic flow incites the transition. Received 20 August 2001     

Rb atomic absorption line reference for single Sr+ laser cooling systems

85 Rb, 5s²S_1/2(F”=2)→6p²P_1/2(F’=2,3) absorption resonance with the ⁸⁸Sr⁺, 5s²S_1/2→5p²P_1/2 transition is exploited to provide a simple, effective frequency reference for a laser cooling/fluorescence excitation source applied to single Sr⁺ ions. A modulation-free frequency stabilization system has been designed which uses the differential signal from two frequency-displaced beams traversing a Rb cell and which probe the Doppler-broadened Rb S–P lineshape at microwatt power levels. The method is applied to frequency lock a 422-nm frequency-doubled diode laser system that is used for excitation of a single ⁸⁸Sr⁺ ion. Stable, long-term laser cooling and fluorescence are achieved using the frequency-stabilized 422-nm source resulting in observed ion confinement times without adjustment of over 8 h, together with an improvement in single-ion loading efficiency. Received: 12 February 1998     

A rubidium-stabilized ring-cavity resonator for optical frequency metrology: precise measurement of the D1 line in 133Cs

We have developed a ring-cavity resonator that can be used to measure the absolute frequencies of optical transitions with an uncertainty below 40 kHz. The length of the resonator is calibrated against a reference laser locked to the D₂ line of ⁸⁷Rb, the frequency of which is known with 6 kHz accuracy. We demonstrate the power of this technique by measuring the absolute frequencies of various hyperfine transitions in the D₁ line of ¹³³Cs. Our results agree with earlier measurements using the frequency-comb technique, and have similar accuracy. Measurement of the D₁-line frequency could lead to a more precise determination of the fine-structure constant. We also report a precise value of A=291.918(8) MHz for the hyperfine constant in the 6P_1/2 state.     

Extended morphometric analysis of neuronal cells with Minkowski valuations

Minkowski valuations provide a systematic framework for quantifying different aspects of morphology. In this paper we apply vector- and tensor-valued Minkowski valuations to neuronal cells from the cat's retina in order to describe their morphological structure in a comprehensive way. We introduce the framework of Minkowski valuations, discuss their implementation for neuronal cells and show how they can be used to characterize cells of different morphological categories. We also provide a comparison to a Sholl analysis.     

Analysis of Vertex D^＊D^＊ρ with Light-Cone QCD Sum Rules

We analyse the vertex D^＊D^＊ρ with the light-cone QCD sum rules. The strong coupling constant gD^＊D^＊ρ is an important parameter in evaluating the charmonium absorption cross sections in searching for the quark-gluon plasmas. Our numerical value for the gD^＊D^＊ρ is consistent with the prediction of the effective SU（4） symmetry and vector meson dominance theory.     

Empirical transverse charge densities in the deuteron

Using the recent empirical information on the deuteron electromagnetic form factors we map out the transverse charge density in the deuteron as viewed from a light front moving towards the deuteron. The charge densities for a transversely polarized deuteron are characterized by monopole, dipole and quadrupole patterns.     

Neutrino mixing discriminates geo-reactor models

Geo-reactor models suggest the existence of natural nuclear reactors at different deep-earth locations with loosely defined output power. Reactor fission products undergo beta decay with the emission of electron antineutrinos, which routinely escape the earth. Neutrino mixing distorts the energy spectrum of the electron antineutrinos. Characteristics of the distorted spectrum observed at the earth's surface could specify the location of a geo-reactor, discriminating the models and facilitating more precise power measurement.