50 research outputs found
Temperature changes in the excitonic absorption band in flat double nanoheterostructures GaAs/AlxGa₁₋xAs
Adduced in this paper are the method and results of theoretical studying the effects of spatial confinement and exciton-phonon interaction on the position and shape of the excitonic absorption band in flat double nanoheterostructures GaAs/AlxGa₁₋xAs. The heterojunction has been considered as unstrained, the nanosystem is modeled as a rectangular quantum well of a finite depth. Interaction of exciton with optical polarization phonons has been taken into account. Calculated has been the temperature dependence of the energy corresponding to transition into the background excitonic state, and determined have been temperature changes in the absorption coefficient related with this transition. It has been shown that observation of these temperature changes in the energy and absorption coefficient, caused by interaction with optical phonons, is possible in the case of exciton with heavy hole at temperatures above 100 K
Temperature changes of the exciton transition energy in lead di-iodide nanofilms
Adduced in this work are the results of theoretical investigations devoted to
the influence of spatial confinement effects, self-polarization of heterojunction planes
and exciton-phonon interaction on values of the exciton transition energy in lead diiodide
nanofilms placed into dielectric ambience (glass or polymer). The heterojunction
is considered to be unloaded, nanosystem is modeled with an infinite deep quantum well
and characterized by an essential difference between dielectric permeabilities in both
sides of the heterojunction. Calculated in the work are dependences of the exciton energy
on the nanofilm thickness and temperature. The results of calculations are in accordance
with the known data of experimental measurements
Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications
The aim of the paper is to show the potential of the spectroscopic ellipsometry and magnetooptical (MO) spectroscopy for probing of the multilayered films (MLF) with sublayer thickness of about a few nanometres. The main approach applied by us is based on the comparison of the experimental optical and MO properties with the simulated ones based on various models of the MLF. Specifically, as shown, such an approach can be useful for studying the nature of unusual MO properties and the interfaces in MLF comprising the noble and 3d-transition metals (3d-TM). The high sensitivity of the applied spectroscopic methods for the monitoring of the solid-state reactions in the 3d-TM/Si MLF induced by ion-beam treatment or by thermal annealing is also demonstrated. The optical properties of various silicides formed spontaneously or induced by various treatments at interfaces are evaluated experimentally and compared with the results of first-principle calculations.В данной работе показаны возможности спектральной эллипсометрии и магнитооптической (МО) спектроскопии для изучения структуры и особенностей физических свойств многослойных металлических пленок (МСП) с толщинами составляющих слоев порядка единиц нанометров. Основной подход исследования базируется на сравнении экспериментально измеренных оптических и МО свойств МСП с модельными, полученными для различных моделей структуры МСП. Было показано, что данный подход позволяет выяснить природу необычных МО свойств, а также структуру интерфейсной области в МСП, состоящих из слоев благородных и 3d-переходных металлов (ПМ). Также в работе продемонстрирована высокая чувствительность спектральной эллипсометрии для изучения твердотельных реакций в МСП 3d-ПМ/Si, вызванных ионной бомбардировкой или термическим отжигом. Оптические свойства различных силицидов 3d-ПМ, сформированных спонтанно либо в результате различных воздействий на МСП, были изучены экспериментально и сравнены с результатами теоретических первопринципных расчетов.В даній роботі показані можливості спектральної еліпсометрії та магнітооптичної (МО) спектроскопії для вивчення структури та особливостей фізичних властивостей багатошарових металевих плівок (БШП) з товщинами складаючих їх шарів порядку одиниць нанометрів. Основний підхід дослідження базується на порівнянні експериментально одержаних оптичних та МО властивостей БШП з модельними, що були одержані для різних моделей структури БШП. Було показано, що даний підхід дозволяє визначити природу незвичайних МО властивостей, а також природу інтерфейсної області БШП, що складаються з шарів благородних та 3d-перехідних металів (ПМ). В роботі також паказана висока чутливість спектральної еліпсометрії для вивчення твердотільних реакцій в БШП 3d-ПМ/Si, зумовлених іонним бомбардуванням або термічним відпалом. Оптичні властивості різних силіцидів 3d-ПМ, що було зформовані спонтанно або завдяки зовнішньому впливу, були вивчені експериментально та порівняні з результатами теоретичних першопринципних розрахунків
Charge-Symmetry Violation in Pion Scattering from Three-Body Nuclei
We discuss the experimental and theoretical status of charge-symmetry
violation (CSV) in the elastic scattering of pi+ and pi- on 3H and 3He.
Analysis of the experimental data for the ratios r1, r2, and R at Tpi = 142,
180, 220, and 256 MeV provides evidence for the presence of CSV. We describe
pion scattering from the three-nucleon system in terms of single- and
double-scattering amplitudes. External and internal Coulomb interactions as
well as the Delta-mass splitting are taken into account as sources of CSV.
Reasonable agreement between our theoretical calculations and the experimental
data is obtained for Tpi = 180, 220, and 256 MeV. For these energies, it is
found that the Delta-mass splitting and the internal Coulomb interaction are
the most important contributions for CSV in the three-nucleon system. The CSV
effects are rather sensitive to the choice of pion-nuclear scattering
mechanisms, but at the same time, our theoretical predictions are much less
sensitive to the choice of the nuclear wave function. It is found, however,
that data for r2 and R at Tpi = 142 MeV do not agree with the predictions of
our model, which may indicate that there are additional mechanisms for CSV
which are important only at lower energies.Comment: 26 pages of RevTeX, 16 postscript figure
Photo- and thermally-induced changes in the optical properties of Ge-S-Se amorphous films
The optical transmissions spectra of amorphous Ge-S-Se films of chemical
compositions (GeS₂)₅₀(GeSe₂)₅₀ and (GeS₃)₅₀(GeSe₃)₅₀, prepared by thermal evaporation,
have been measured over the whole 400 to 800 nm spectral range. It has been ascertained
that annealing of the films leads to the absorption edge shift into the short-wave spectral
region. The values of pseudo-gap width Eg and film refraction index n have been
determined. Changes in optical properties of films are caused by structural
transformations taking place in them under laser illumination and annealing
Recording the high efficient diffraction gratings by using He-Cd laser
High efficient holographic diffraction gratings with spatial frequencies from 600 to 3600 mm⁻¹ have been recorded using As₄₀S₆₀–хSeх (х = 0, 10, 20) photoresist layers and He-Cd laser operating at the wavelength λ = 440 nm. The investigation of the grating relief made by atomic force microscopy revealed that As₄₀S₆₀–хSeх resists allows one to record grating originals with profiles of various heights depending on the resist chemical composition, its etching and exposure times. We obtained typical spectral and angular dependences of the first order diffraction efficiency for the grating with the high modulation depth and groove profile close to the sinusoidal one. Comparing the recorded gratings with different spatial frequencies, exposure and etching times, we determined optimal recording conditions (exposure and etching times) in order to obtain gratings with the high diffraction efficiency
Measurement of and between 3.12 and 3.72 GeV at the KEDR detector
Using the KEDR detector at the VEPP-4M collider, we have measured
the values of and at seven points of the center-of-mass
energy between 3.12 and 3.72 GeV. The total achieved accuracy is about or
better than at most of energy points with a systematic uncertainty of
about . At the moment it is the most accurate measurement of in
this energy range
Search for narrow resonances in e+ e- annihilation between 1.85 and 3.1 GeV with the KEDR Detector
We report results of a search for narrow resonances in e+ e- annihilation at
center-of-mass energies between 1.85 and 3.1 GeV performed with the KEDR
detector at the VEPP-4M e+ e- collider. The upper limit on the leptonic width
of a narrow resonance Gamma(R -> ee) Br(R -> hadr) < 120 eV has been obtained
(at 90 % C.L.)
Measurement of relative branching fractions of B decays to and mesons
The relative rates of B-meson decays into and mesons are
measured for the three decay modes in pp collisions recorded with the LHCb
detector. The ratios of branching fractions () are measured to be
,
,
where the third uncertainty is from the ratio of the and
branching fractions to .Comment: 14 pages, 1 figur