Electronic Structure of O-D Exciton Ground State in CdSe Nanocrystals

1996 ◽  
Vol 452 ◽  
Author(s):  
M. Chamarro ◽  
M. Dib ◽  
C. Gourdon ◽  
P. Lavallard ◽  
O. Lublinskaya ◽  
...  
Keyword(s):  
Ground State ◽  
Cdse Nanocrystals ◽  
Photoluminescence Excitation ◽  
Photoluminescence Band ◽  
Excitation Spectra ◽  
Shape Dependence ◽  
Theoretical Predictions ◽  
Narrow Energy Range ◽  
Shape And Size ◽  
Good Agreement

AbstractWe present results on photoluminescence excitation spectra (PLE) of wurtzite CdSe nanocrystals (NCs) embedded in a glass with effective radii in the range 15–35 Å. Information on the near band-gap absorption of an assembly of NCs is obtained by selecting a narrow energy range in the inhomogeneously broadened photoluminescence band. The size and shape dependence of the lowest exciton states are calculated for slightly non-spherical wurtzite NCs. The experimental results are in good agreement with the theoretical predictions when both shape and size dispersions are taken into account.

Resonant Photoluminescence Excitation in GaAs Grown Directly on Si

1988 ◽  
Vol 116 ◽  
Author(s):  
S. Zemon ◽  
C. Jagannath ◽  
S. K. Shastry ◽  
W. J. Miniscalco ◽  
G. Lambert
Keyword(s):  
Ground State ◽  
Heavy Hole ◽  
Laser Excitation ◽  
Free Exciton ◽  
Light Hole ◽  
The Other ◽  
Organometallic Vapor Phase Epitaxy ◽  
Photoluminescence Excitation ◽  
Excitation Spectra ◽  
Excitation Line

AbstractWe describe new results observed during resonant excitation in the excitonic region of GaAs grown directly on Si by organometallic vapor phase epitaxy. Two resolved features were found in the light hole photoluminescence (PL) region, one identified with a free exciton process and the other with donor-related transitions. Features which track the laser excitation line were observed and identified with a process in which a donor is excited from the n=l ground state to an n=2 excited state. The PL excitation spectra associated with these features have spectral widths as narrow as 1.5 meV. PL spectral widths of ~3 meV have been attained for the heavy hole exciton band, representing the narrowest value obtained for OMVPE material and an improvement of about 30% over our best previous results.

High Resolution Site-Selective Studies of Erbium-Centers in GaN and GaN:Mg.

2005 ◽  
Vol 866 ◽  
Author(s):  
V. Glukhanyuk ◽  
H. Przybylińska ◽  
A. Kozanecki ◽  
W. Jantsch
Keyword(s):  
High Resolution ◽  
Point Charge ◽  
Energy Levels ◽  
Photoluminescence Excitation ◽  
Excitation Spectra ◽  
Point Charge Model ◽  
Mg Doping ◽  
Charge Model ◽  
Site Selective ◽  
Good Agreement

AbstractIn this work the high resolution optical spectroscopy is used in order to determine the positions of the Stark split 4I15/2, 4I11/2 and 4I9/2 energy levels of Er3+ in GaN and GaN:Mg. Photoluminescence and photoluminescence excitation spectra were measured at energies corresponding to the 4I15/2→4I9/2 and 4I15/2→4I11/2 absorption transitions. Low Er implant doses were applied to reduce the number of possible defects. In undoped GaN only a single Er-center was observed and no influence of Mg doping on the energy level splittings of this center in GaN:Mg was found. Numerical analysis based on point charge model was used to calculate parameters of the local crystal field (CF) acting on Er3+ ions. The splittings of the 4I9/2 and 4I11/2 energy levels were calculated in weak CF approach and good agreement with experimental results was obtained. The calculations confirmed that the symmetry of the erbium center in hexagonal GaN is C3v.

scholarly journals Room temperature excitation spectroscopy of single quantum dots

2011 ◽  
Vol 2 ◽  
pp. 516-524 ◽  
Author(s):  
Christian Blum ◽  
Frank Schleifenbaum ◽  
Martijn Stopel ◽  
Sébastien Peter ◽  
Marcus Sackrow ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Single Molecule ◽  
Room Temperature ◽  
Cdse Nanocrystals ◽  
Photoluminescence Excitation ◽  
Single Quantum ◽  
Excitation Spectra ◽  
Detection Scheme ◽  
Single Quantum Dots ◽  
The Individual

We report a single molecule detection scheme to investigate excitation spectra of single emitters at room temperature. We demonstrate the potential of single emitter photoluminescence excitation spectroscopy by recording excitation spectra of single CdSe nanocrystals over a wide spectral range of 100 nm. The spectra exhibit emission intermittency, characteristic of single emitters. We observe large variations in the spectra close to the band edge, which represent the individual heterogeneity of the observed quantum dots. We also find specific excitation wavelengths for which the single quantum dots analyzed show an increased propensity for a transition to a long-lived dark state. We expect that the additional capability of recording excitation spectra at room temperature from single emitters will enable insights into the photophysics of emitters that so far have remained inaccessible.

N.M.R.-Studies of Bond Order in Azulene, Biphenylene and 1,6-Methano[10]annulene

1990 ◽  
Vol 43 (9) ◽  
pp. 1541 ◽  
Author(s):  
MJ Collins ◽  
S Sternhell ◽  
CW Tansey
Keyword(s):  
Experimental Data ◽  
Ground State ◽  
Bond Order ◽  
Membered Ring ◽  
Coupling Constants ◽  
Bond Orders ◽  
Bond Lengths ◽  
Theoretical Predictions ◽  
Electron Distributions ◽  
Good Agreement

The 4J(H-C-C-Me) coupling constants of methyl-substituted derivatives, probes of bond order, have been used to examine the ground-state π- electron distributions in azulene (1), biphenylene (2) and 1,6- methano [10] annulene (3). The experimental data obtained are in good agreement with theoretical predictions for biphenylene (2) and provide some evidence for π-electron disproportionation towards the five-membered ring in azulene (1). The bond orders in 1,6-methano [10] annulene (3) obtained in this work are at variance with those predicted on the grounds of bond lengths.

Room-Temperature Chemical Synthesis of C2

2019 ◽  
Author(s):  
Kazunori Miyamoto ◽  
Shodai Narita ◽  
Yui Masumoto ◽  
Takahiro Hashishin ◽  
Mutsumi Kimura ◽  
...  
Keyword(s):  
Chemical Synthesis ◽  
Ground State ◽  
Room Temperature ◽  
Chemical Species ◽  
Quadruple Bond ◽  
Photon Excitation ◽  
Physical Energy ◽  
Theoretical Predictions ◽  
Carbon Arc ◽  
Inherent Nature

Diatomic carbon (C<sub>2</sub>) is historically an elusive chemical species. It has long been believed that the generation of C<sub>2 </sub>requires extremely high “physical” energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C<sub>2 </sub><i>in the ground state </i>is experimentally inaccessible. Here, we present the first “chemical” synthesis of C<sub>2 </sub>in a flask at <i>room temperature or below</i>, providing the first experimental evidence to support theoretical predictions that (1) C<sub>2 </sub>has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that (2) C<sub>2 </sub>serves as a molecular element in the formation of sp<sup>2</sup>-carbon allotropes such as graphite, carbon nanotubes and C<sub>60</sub>.

scholarly journals Effects of selenisation temperature on photoluminescence and photoluminescence excitation spectra of ZnO/CdS/Cu2ZnSnSe4/Mo/glass

2019 ◽  
Vol 672 ◽  
pp. 146-151 ◽  
Author(s):  
M.A. Sulimov ◽  
M.V. Yakushev ◽  
J. Márquez-Prieto ◽  
I. Forbes ◽  
P.R. Edwards ◽  
...  
Keyword(s):  
Photoluminescence Excitation ◽  
Excitation Spectra

scholarly journals A Generalized Approach for Evaluating the Mechanical Properties of Polymer Nanocomposites Reinforced with Spherical Fillers

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 830
Author(s):  
Julio Cesar Martinez-Garcia ◽  
Alexandre Serraïma-Ferrer ◽  
Aitor Lopeandía-Fernández ◽  
Marco Lattuada ◽  
Janak Sapkota ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Polymeric Nanocomposites ◽  
Mechanical Reinforcement ◽  
Future Studies ◽  
Three Phase ◽  
Theoretical Predictions ◽  
Filler Network ◽  
New Research ◽  
Good Agreement ◽  
Research Avenue

In this work, the effective mechanical reinforcement of polymeric nanocomposites containing spherical particle fillers is predicted based on a generalized analytical three-phase-series-parallel model, considering the concepts of percolation and the interfacial glassy region. While the concept of percolation is solely taken as a contribution of the filler-network, we herein show that the glassy interphase between filler and matrix, which is often in the nanometers range, is also to be considered while interpreting enhanced mechanical properties of particulate filled polymeric nanocomposites. To demonstrate the relevance of the proposed generalized equation, we have fitted several experimental results which show a good agreement with theoretical predictions. Thus, the approach presented here can be valuable to elucidate new possible conceptual routes for the creation of new materials with fundamental technological applications and can open a new research avenue for future studies.

VMC CALCULATIONS OF THE GROUND STATE PROPERTIES OF NUCLEAR MATTER

2005 ◽  
Vol 14 (02) ◽  
pp. 255-267 ◽  
Author(s):  
KAAN MANİSA ◽  
ÜLFET ATAV ◽  
RIZA OGUL
Keyword(s):  
Nuclear Matter ◽  
Ground State ◽  
Nucleon Nucleon ◽  
Neutron Matter ◽  
Potential Term ◽  
Ground State Properties ◽  
Dependent Potential ◽  
Variational Monte Carlo Method ◽  
Kinetic And Potential Energies ◽  
Good Agreement

A Variational Monte Carlo method (VMC) is described for the evaluation of the ground state properties of nuclear matter. Equilibrium properties of symmetric nuclear matter and neutron matter are calculated by the described VMC method. The Urbana ν14 potential is used for the nucleon–nucleon interactions in the calculations. Three- and more-body interactions are included as a density dependent potential term. Total, kinetic and potential energies per particle are obtained for nuclear and neutron matter. Pressure values of nuclear and neutron matter are also calculated at various densities. The binding energy of nuclear matter is found to be -16.06 MeV at a saturation density of 0.16 fm -3. The results obtained are in good agreement with those obtained by various authors with different potentials and techniques.

The Reduction of Bias Error in Transfer Function Estimates Using FFT-Based Analyzers

1984 ◽  
Vol 106 (1) ◽  
pp. 29-35 ◽  
Author(s):  
P. Cawley
Keyword(s):  
Transfer Function ◽  
Random Excitation ◽  
Analogue Computer ◽  
Bias Error ◽  
Testing Time ◽  
Theoretical Predictions ◽  
Set Up ◽  
Modal Mass ◽  
Time Required ◽  
Good Agreement

The susceptibility to bias error of two methods for computing transfer (frequency response) functions from spectra produced by FFT-based analyzers using random excitation has been investigated. Results from tests with an FFT analyzer on a single degree-of-freedom system set up on an analogue computer show good agreement with the theoretical predictions. It has been shown that, around resonance, the bias error in the transfer function estimate H2 (Syy/Sxy*) is considerably less than that in the more commonly used estimate, H1 (Sxy/Sxx). The record length, and hence the testing time, required for a given accuracy is reduced by over 50 percent if the H2 calculation procedure is used. The analysis has also shown that if shaker excitation is used on lightly damped structures with low modal mass, it is important to minimize the mass of the force gage and the moving element of the shaker.

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