Optical response of a δ-layer capacitor

The fabrication of two δ-layers of opposite polarity in a semiconductor constitutes a capacitor. The charge on each "plate" may be modified by photogenerating carriers to screen the dopant ions, which alters the field between them. This has the effect of changing the transition energies between confined states in the structure, which results in a substantial (60 meV) blue shift, which may be utilised in a modulator structure. These effects have been investigated using steady-state and time-resolved photoluminescence, in conjunction with band modelling.     

Dynamics of a cold quantum gas in a δ-split one-dimensional potential well

Dynamics of a wave function in a non-symmetrically split (spatially asymmetric) doublewell potential is considered. We study the dependence of the probability of well-to-well transitions on the degree of spatial asymmetry of well sizes and show that the quantum tunneling between the wells is significantly suppressed by this asymmetry. Practically complete suppression occurs at five-ten percent asymmetry. This is close to the threshold of sensitivity of contemporary experimental schemes for creating two-well potentials. We predict the phenomenon of resonance in quantum tunneling of considered states. We have also shown that an incoherently prepared superposition state tunnels in a double-well potential almost in the same way as a perfectly coherent state.     

Radiative characteristics of a two-section laser structure based on a δ-doping superlattice

Spectral characteristics of a two-section laser structure with δ-doping active regions are studied theoretically. The wide range of tuning of the lasing wavelength is primarily related to specific characteristics of the gain spectra of n-i-p-i crystals: the dependence of the effective band-gap width of the superlattice on the level of excitation, the character of variation of the overlap integrals of the electron and hole wave functions, and broadening of the electronic spectra due to fluctuations of the electrostatic potential. Depending on the pumping currents in sections of the laser structure, the lasing wavelength can be tuned over a wide spectral range of the IR region in regimes of cw lasing, the transient regime, and the regime of regular pulsations. In the regime of self-sustaining pulsations, lasing is also possible at two wavelengths spaced well apart.     

Noninertial feedback detection of a random process using a Schottky diode with δ-doping

The problem of determining the average value and dispersion of the process during the noninertial detection of a random stationary process, with the feedback taken into account, using a Schottky diode with δ-doping is investigated. The dependence of the output parameters on the input ones has been obtained in the Gaussian approximation.     

Effect of Magnetic Field on a p-Type δ-Doped GaAs Layer

The energy levels of holes in a p-type δ-doped GaAs structure under a magnetic field are theoretically calculated within the framework of the effective mass approximation for a uniform aceeptor distribution. The electronic structure is calculated by solving the Schrodinger and Poisson equations self-consistently. The effect of the magnetic field on the potential profile changes the degree of the confinement and localization, and thus this behavior can be used to study these systems in regions of interest, without the need to grow many different samples. It is found that the heavy-hole subbands contain many more energy states than the light-hole ones; the population of the heavy-hole levels represents approximately 91 % of all the carriers without magnetic field. With increasing magnetic field the total population of the heavy-holes increases and the number of filled states changes.     

Accuracy and precision of a laser-spectroscopy approach to the analysis of δ2H and δ18O in human urine

The isotope ratio analysis of body water often involves large sample numbers and lengthy sample processing. Here we demonstrate the ability of isotope ratio infrared spectroscopy (IRIS) to rapidly and accurately analyse the isotope ratios of water in urine. We analysed water extracted from human urine using traditional isotope ratio mass spectrometry (IRMS) and compared those values with IRIS-analysed extracted water and un-extracted urine. Regression analyses for δ²H and δ¹⁸O values between (1) extracted water analysed via IRMS and IRIS and (2) urine and extracted water analysed via IRIS were significant (R ²=0.99). These results indicate that cryogenic distillation of urine was not required for an accurate estimate of the isotopic composition of urine when using IRIS.     

Accuracy and precision of a laser-spectroscopy approach to the analysis of δ²H and δ¹⁸O in human urine

The isotope ratio analysis of body water often involves large sample numbers and lengthy sample processing. Here we demonstrate the ability of isotope ratio infrared spectroscopy (IRIS) to rapidly and accurately analyse the isotope ratios of water in urine. We analysed water extracted from human urine using traditional isotope ratio mass spectrometry (IRMS) and compared those values with IRIS-analysed extracted water and un-extracted urine. Regression analyses for δ2H and δ1?O values between (1) extracted water analysed via IRMS and IRIS and (2) urine and extracted water analysed via IRIS were significant (R2=0.99). These results indicate that cryogenic distillation of urine was not required for an accurate estimate of the isotopic composition of urine when using IRIS.     

Screening in a δ-doped semiconductor

The screening of an impurity in the quasi-two-dimensional (2D) electron gas in a δ-doped semiconductor structure is investigated. The screened impurity matrix elements are calculated and compared using three different approaches: the 2D random phase approximation (RPA), the corresponding 2D Thomas–Fermi theory and a quasi-three-dimensional (3D) Yukawa-like screening model. It is found that the 2D Thomas–Fermi theory differs from the RPA result, even in the limit of low q vectors, if more than one subband is occupied. This result is explained analytically by closely examining theq → 0 limit of the dielectric tensor. The 2D Thomas–Fermi theory is shown to represent a poor approximation to the RPA whereas the quasi-3D screening model agrees well with the RPA results for not too smallqvectors. Furthermore, this model reduces computing times by orders of magnitude in comparison with the RPA. Thus, our 3D screening model considerably simplifies the calculation of impurity scattering rates in the investigation of the electron mobility in a δ-doping layer.     

Hydrogen-Bond Symmetrization of δ-AlOOH

The δ-AIOOH can transport water into the deep mantle along cold subducting slab geothenn. We investigate the hydrogen-bond symmetrization behavior of δ-AIOOH under the relevant pressure-temperature condition of the lower mantle using ab initio molecular dynamics(AID). The static symmetrization pressure of 30.0 GPa can be reduced to 17.0 GPa at 300 K by finite-temperature(T) statistics, closer to the experimental observation of-10.0 GPa. The symmetrization pressure obtained by MD simulation is related to T by P(GPa) = 13.9(GPa) +0.01(GPa/K) × T(K). We conclude that δ-AIOOH in the lower mantle exists with symmetric hydrogen bond from its birthplace, or someplace slightly deeper, to the core-mantle boundary(CATB) along cold subducting slab geotherm. The bulk modulus decreases with T and increases anomalously upon symmetrization: K_o(GPa) =181(GPa)-0.013(GPa/K) × T(K) for δ-AIOOH with asymmetric hydrogen bond, and K_o(GPa) = 216(GPa)-0.013(GPa/K) × T(K) for δ-AIOOH with symmetric hydrogen bond. Our results provide an important insight into the existent form and properties of δ-AIOOH in the lower mantle.     

Manipulating transition of a two-component Bose–Einstein condensate with a weak δ-shaped laser

We theoretically study the transition dynamics of a two-component Bose–Einstein condensate driven by a train of weak δ-shaped laser pulses. We find that the atomic system can experience peculiar resonant transition even under weak optical excitations and derive the resonance condition by the perturbation method. Employing this mechanism, we propose a scheme to obtain an atomic ensemble with desired odd/even atom number and also a scheme to prepare a nonclassical state of the many-body system with fixed atom number.     

Stability and Symmetry-Breaking Bifurcation for the Ground States of a NLS with a δ′ Interaction

We determine and study the ground states of a focusing Schrödinger equation in dimension one with a power nonlinearity |ψ|^2μ ψ and a strong inhomogeneity represented by a singular point perturbation, the so-called (attractive) δ′ interaction, located at the origin. The time-dependent problem turns out to be globally well posed in the subcritical regime, and locally well posed in the supercritical and critical regime in the appropriate energy space. The set of the (nonlinear) ground states is completely determined. For any value of the nonlinearity power, it exhibits a symmetry breaking bifurcation structure as a function of the frequency (i.e., the nonlinear eigenvalue) ω. More precisely, there exists a critical value ω* of the nonlinear eigenvalue ω, such that: if ω₀ <  ω <  ω*, then there is a single ground state and it is an odd function; if ω >  ω* then there exist two non-symmetric ground states. We prove that before bifurcation (i.e., for ω <  ω*) and for any subcritical power, every ground state is orbitally stable. After bifurcation (ω = ω^* + 0), ground states are stable if μ does not exceed a value ${\mu^\star}$ that lies between 2 and 2.5, and become unstable for μ > μ*. Finally, for μ >  2 and ${\omega \gg \omega^*}$ , all ground states are unstable. The branch of odd ground states for ω <  ω* can be continued at any ω >  ω*, obtaining a family of orbitally unstable stationary states. Existence of ground states is proved by variational techniques, and the stability properties of stationary states are investigated by means of the Grillakis-Shatah-Strauss framework, where some non-standard techniques have to be used to establish the needed properties of linearization operators.     

Extraction of Surface Roughness from the Central δ-peak of Light Scattering Using a Multi-wavelength Ar~ Laser

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｓｏｍｅｕｓｅｃｏｎｔａｃｔｔｅｃｈｎｉｑｕｅｓ(ｓｕｃｈａｓｐｒｏｆｉｌｏｍｅｔｒｙ,ｓｃａｎｎｉｎｇｐｒｏｂｅｍｉｃｒｏｓｃｏｐｙ)ａｎｄｔｈｅｏｔｈｅｒｓｕｓｅｎｏｎｃｏｎｔａｃｔｔｅｃｈｎｉｑｕｅｓ,ｍｏｓｔｏｆｗｈｉｃｈａｒｅａｃｔｕａｌｌｙｏｐｔｉｃａｌｍｅｔｈｏｄｓ,ａｎｄｌｉｇｈｔｓｃａｔｔｅｒｉｎｇ[1,2],ｅｌｌｉｐｓｅｏｍｅｔｒｙ[3]ａｎｄｓｕｒｆａｃｅｐｌａｓｍｏｎｓｐｅｃｔｒｏｓｃｏｐｙ[4]ａｒｅｔｈｅｅｘａｍｐｌｅｓ.Ｕｐｔｏｎｏｗ,ｔｈｅｄｅｔｅｒ…     

USGS48 Puerto Rico precipitation – a new isotopic reference material for δ2H and δ18O measurements of water

A new secondary isotopic reference material has been prepared from Puerto Rico precipitation, which was filtered, homogenised, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and calibrated by dual-inlet isotope-ratio mass spectrometry. This isotopic reference material, designated as USGS48, is intended to be one of two isotopic reference waters for daily normalisation of stable hydrogen (δ²H) and stable oxygen (δ¹⁸O) isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. The δ²H and δ¹⁸O values of this reference water are?2.0±0.4 and?2.224±0.012 ‰, respectively, relative to Vienna Standard Mean Ocean Water on scales normalised such that the δ²H and δ¹⁸O values of Standard Light Antarctic Precipitation reference water are?428 and?55.5 ‰, respectively. Each uncertainty is an estimated expanded uncertainty (U=2u_c) about the reference value that provides an interval that has about a 95 % probability of encompassing the true value. This isotopic reference water is available by the case of 144 glass ampoules containing 5 mL of water in each ampoule.     

Parity operator and quantization of δ-functions

In the Weyl quantization scheme, the -function at the origin of phase space corresponds to the parity operator. The quantization of a functionf() on phase space is the operator f(/2)W()dM, whereM is the parity andW() the Weyl operator.     

Determination of δ13 CV−PDB and δ15NAIR values of cocaine from a big seizure in Germany by stable isotope ratio mass spectrometry†

In this study, δ¹³C_{V? PDB} and δ¹⁵N_AIR values of 132 cocaine samples from a big seizure in Germany in 2002 were determined using elemental analyser isotope ratio mass spectrometry. The 1.2 tons of cocaine were packed in 1 kg packages and the cocaine bricks inside these packages showed certain logos. Twenty different logos could be identified. Results show a large variability among some samples, for δ¹⁵N_AIR values ranging from?17 to ?2 ‰. Furthermore, the possibility of linking samples with the same logo was checked. The results show that, in general, there is no relationship between the determined isotope ratio and a certain logo.     

High-precision measurements of δ2H, δ18O and δ17O in water with the aid of cavity ring-down laser spectroscopy

A thorough evaluation of measurement uncertainty together with control of short-term and long-term precision of measurements should be a basis of any successful quality assurance/quality control (QA/QC) strategy aimed at maintaining a high quality of the analytical process. Here we present the results of a comprehensive assessment of the analytical performance of a Picarro L2140-i CRDS laser spectrometer analysing δ²H, δ¹⁸O and δ¹⁷O in water. The assessment is based on results obtained during 15 months of continuous operation of this instrument (February 2017 to May 2018). The short-term precision of measured and derived quantities was 0.11, 0.036, 0.028, 0.23 ‰ and 11 per meg, for δ²H, δ¹⁸O, δ¹⁷O, d-excess and Δ¹⁷O, respectively, and is comparable to the precision reported by the manufacturer. The long-term precision of the L2140-i, defined as standard uncertainty of the time series of 153 analyses of a laboratory standard conducted throughout 15 months, was roughly two times lower (0.24, 0.053, 0.038, 0.37 ‰ and 21 per meg, for δ²H, δ¹⁸O, δ¹⁷O, d-excess and Δ¹⁷O). In-depth assessment of the measurement uncertainty of a single analysis revealed that assigned uncertainty of the calibration standards is an important component of the uncertainty budget, especially in case of δ²H analysis.     

Resonant Multichannel Scattering in a Nanotube with δ-Potentials

The resonant tunneling transmission of an electron through the quantum wire comprising two three-dimensional δ-potentials located along the nanotube axis is considered. Using the formulas obtained recently for amplitudes of multichannel scattering, the condition (equation) of resonance is found for the multichannel scattering, at which the system under consideration becomes completely transparent for motion of the electron. A procedure based on the method of vector diagrams is proposed for simplification of the resonance equation. It is shown that if the initial energy of longitudinal motion is insufficient for excitation of new scattering channels, then the resonance equation coincides with the corresponding equation of one-dimensional problem.