Optical absorption in gold caused by a granular dielectric overlayer

1991 ◽  
Vol 69 (2) ◽  
pp. 107-113 ◽  
Author(s):  
Vo-Van Truong ◽  
P. V. Ashrit ◽  
G. Bader ◽  
P. Courteau ◽  
F. E. Girouard ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Surface Plasmons ◽  
Dielectric Layer ◽  
Effective Medium Theory ◽  
Polarized Light ◽  
Dipole Approximation ◽  
Mirror Image ◽  
Attenuated Total Reflection ◽  
Metallic Surface ◽  
Absorption Feature

Light can be used to excite surface plasmons if there are proper mechanisms for coupling with those surface plasmons. This coupling can usually be achieved via surface roughness or evanescent waves in attenuated total-reflection experiments. In the present work, we report evidence of the possibility of having a resonant optical absorption when a granular dielectric layer is deposited on a metallic surface. Very thin films of MgF2 of mass thickness up to 8 nm have been used as a discontinuous overcoat on Au films of 100 nm thickness. Reflectivity measurements with p-polarized light incident at 40° show a resonant-type absorption near 520 nm when the dielectric layer is added to the Au surface. As the MgF2 film grows thicker and becomes continuous this absorption feature is no longer prominent. To account for this phenomenon, an effective-medium theory is used to describe the optical behavior of the coated Au surface. By including mirror-image effects in the dipole approximation, basic features of experimental measurements can be reproduced.

scholarly journals Radiation-Induced Correlation between Molecules Nearby Metallic Antenna Array

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Yoshiki Osaka ◽  
Nobuhiko Yokoshi ◽  
Hajime Ishihara
Keyword(s):  
Optical Absorption ◽  
Surface Plasmons ◽  
Approximation Method ◽  
Photon Emission ◽  
Peak Shift ◽  
Dipole Approximation ◽  
Spectral Peak ◽  
Localized Surface Plasmons ◽  
Radiation Induced ◽  
The Individual

We theoretically investigate optical absorption of molecules embedded nearby metallic antennas by using discrete dipole approximation method. It is found that the spectral peak of the absorption is shifted due to the radiation-induced correlation between the molecules. The most distinguishing feature of our work is to show that the shift is largely enhanced even when the individual molecules couple with localized surface plasmons near the different antennas. Specifically, we first consider the case that two sets of dimeric gold blocks with a spacing of a few nanometers are arranged and reveal that the intensity and spectral peak of the optical absorption strongly depend on the position of the molecules. In addition, when the dimeric blocks and the molecules are periodically arranged, the peak shift is found to increase up to ~1.2 meV (300 GHz). Because the radiation-induced correlation is essential for collective photon emission, our result implies the possibility of plasmon-assisted superfluorescence in designed antenna-molecule complex systems.

scholarly journals Локализованные экситоны в спектре оптического поглощения оксида цинка, легированного марганцем

2019 ◽  
Vol 61 (5) ◽  
pp. 817
Author(s):  
В.И. Соколов ◽  
Н.Б. Груздев ◽  
В.А. Важенин ◽  
А.В. Фокин ◽  
А.В. Дружинин
Keyword(s):  
Zinc Oxide ◽  
Charge Transfer ◽  
Absorption Band ◽  
Optical Absorption ◽  
Absorption Spectra ◽  
Polarized Light ◽  
Threshold Energy ◽  
Impurity Absorption ◽  
Charge Transfer Transitions ◽  
Long Time

AbstractThe results of the study of optical absorption and EPR signals of single crystals of zinc oxide doped with manganese are presented. A broad impurity absorption band with the threshold energy about 2.1 eV, which was treated as a result of charge transfer transitions, has been observed for a long time in ZnO : Mn absorption spectra. In absorption spectra of a polarized light at 4.2 and 77.3 K, we first detected several lines of different intensity in a 1.877–1.936 eV range of energies of the light quanta. The observed lines are attributed to a donor exciton [( d ^5 + h ) e ] that emerges as a result of the Coulomb binding a free s electron and a hole, which is localized on p – d hybridized states. The EPR spectra of Mn^2+ ion signals, when corresponding to the impurity absorption band exposed to light, are found to be not photosensitive. The obtained results indicate that the ZnO : Mn impurity absorption is due to transitions from antibonding p – d hybridized DBH states to the conduction band.

Brief Organic Review

2016 ◽  
Author(s):  
Gary W. Morrow
Keyword(s):  
Functional Groups ◽  
Lewis Acids ◽  
Three Dimensional ◽  
Polarized Light ◽  
Mirror Image ◽  
Bond Line ◽  
Organic Chemical ◽  
Chemical Structures ◽  
Or Groups ◽  
Standard Formalism

In addition to simple hydrocarbon structures (alkanes, alkenes, alkynes, and aromatic systems) and alkyl groups (methyl, ethyl, propyl, isopropyl, etc.), this text assumes a familiarity with the most common functional groups associated with organic chemical structures and their basic reactivity patterns. Table 1.1 summarizes the names and structures of some of the more important functional groups we will be dealing with throughout the remainder of the book. It is important to remember that functional groups containing O or N with nonbonding electrons have an affinity for both protic and Lewis acids and are important participators in H-bonding. Groups containing a carbonyl (C=O) function are especially important, as these bonds are strongly polarized (δ+C=Oδ–), the C atom being electron deficient and the O atom electron excessive; this strong polarization is mainly responsible for the familiar reactivity patterns associated with carbonyl compounds. Figure 1.1 depicts the standard classification of isomers in organic chemical structures. Recall that constitutional isomers are compounds with the same molecular formula but different atom connectivity, such as 1-butanol versus 2-butanol. Stereoisomers, on the other hand, are compounds with the same formula and the same atom connectivity, differing from one another only in the three-dimensional orientation of their atoms in space. These are divided into two groups: enantiomers and diastereomers. Enantiomers are nonsuperimposable mirror image molecules whose asymmetry is usually the result of a tetrahedral carbon atom with four different atoms or groups attached to it, as in the 2-butanol enantiomers. Such chiral molecules rotate the plane of polarized light either (+) or (−) and so are said to be optically active. Achiral molecules, such as 1-butanol, do not rotate the plane of polarized light and so are optically inactive. A standard formalism for representation of a chiral center is to use bond line drawings with two of the four atoms or groups lying in the plane of the paper, a third projecting outward (wedge bond), and the fourth projecting inward (dashed bond).

Cell wall ultrastructure of palm leaf fibers

IAWA Journal ◽  
2014 ◽  
Vol 35 (2) ◽  
pp. 127-137 ◽  
Author(s):  
Shengcheng Zhai ◽  
Yoshiki Horikawa ◽  
Tomoya Imai ◽  
Junji Sugiyama
Keyword(s):  
Cell Wall ◽  
Secondary Wall ◽  
Secondary Xylem ◽  
Polarized Light ◽  
Leaf Sheath ◽  
Mean Value ◽  
Attenuated Total Reflection ◽  
Cellulose Microfibrils ◽  
Palm Species ◽  
Palm Leaf

The cell wall organization of leaf sheath fibers in different palm species was studied with polarized light microscopy (PLM) and transmission electron microscopy (TEM). The secondary wall of the fibers consisted of only two layers, S1 and S2. The thickness of the S1 layer in leaf sheath fibers from the different palm species ranged from 0.31 to 0.90 μm, with a mean value of 0.57 μm, which was thicker than that of tracheids and fibers in secondary xylem of conifers and dicotyledons. The thickness of the S2 layer ranged from 0.44 to 3.43 μm, with a mean value of 1.86 μm. The ratio of S1 thickness to the whole cell wall thickness in palm fibers appears to be higher than in secondary xylem fibers and tracheids. The lignin in the fiber walls is very electron dense which makes it difficult to obtain high contrast of the different layers in the secondary wall. To clarify the cell wall layering with cellulose microfibrils in different orientations, the fibrovascular bundles of the windmill palm (Trachycarpus fortunei) were delignified with different reaction time intervals. The treated fibers were surveyed using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy analysis and TEM. The secondary fiber walls of windmill palm clearly showed only two layers at different reaction intervals with different lignin contents, even after almost all lignin was removed. We suggest that the two-layered structure in the secondary wall of palm leaf fibers, which presumably also applies to the homologous fibers in palm stems, is a specific character different from the fibers in other monocotyledons (such as bamboo and rattan) and dicot wood.

STUDY OF THE OPTICAL ABSORPTION OF Cu CLUSTERS IN THE Cu/ZnO SYSTEM

2001 ◽  
Vol 15 (17n19) ◽  
pp. 625-629 ◽  
Author(s):  
O. VAZQUEZ-CUCHILLO ◽  
A. BAUTISTA-HERNANDEZ ◽  
U. PAL ◽  
L. MEZA-MONTES
Keyword(s):  
Dielectric Constant ◽  
Optical Absorption ◽  
Free Path ◽  
Absorption Spectra ◽  
Effective Medium Theory ◽  
Composite Films ◽  
Mean Free Path ◽  
Optical Absorption Spectra ◽  
Medium Theory ◽  
Coated Nanoparticles

Optical absorption of Cu/ZnO composite films grown by r.f. sputtering are presented. We calculated the optical absorption spectra based on a colloidal-copper model with mean-free-path (MFP) and size corrections to the bulk dielectric constant. All effective-medium theory is used to analyze the presence of the coated nanoparticles and the ZnO matrix. The parameters of the model are fitted to reproduce the experimental spectra.

ANALYTICAL AND NUMERICAL ANALYSIS OF FORCE AND STIFFNESS IN A DIAMAGNETIC BEARING

2009 ◽  
Vol 23 (23) ◽  
pp. 2763-2770 ◽  
Author(s):  
AHMET CANSIZ ◽  
UGUR CEM HASAR
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Levitation Force ◽  
Dipole Approximation ◽  
Mirror Image ◽  
Image Method ◽  
The Finite Element Method ◽  
Stiffness Characteristics ◽  
Ndfeb Permanent Magnet ◽  
Element Method

In this letter, a bearing consisting of a disk-shaped NdFeB permanent magnet levitated by a ferrite magnet with a diamagnetic stabilizer made of two bismuth blocks has been statically analyzed. The analysis, including levitation force and stiffness characteristics of this diamagnetic bearing, has been incorporated with the diamagnetic mirror image method based on the finite element and dipole approximation methods. Force equations of the levitated magnet are derived from the potential of the system in terms of magnetic, diamagnetic and gravitational interactions. The dipole approximation and finite element method were compared with each other. It is observed that while the dipole approximation (an analytical method) is successful in predicting the force and stiffness of the bearing, the finite element method, on the other hand, only estimates the levitation force. It is shown that the dipole approach has advantages over the finite element method for various perspectives such as calculation time and precision.

Electrical and optical investigation of the position of vanadium related defects in the 4H and 6H SiC bandgaps

1996 ◽  
Vol 423 ◽  
Author(s):  
J. R. Jenny ◽  
M. Skowronski ◽  
W. C. Mitchel ◽  
S. R. Smith ◽  
A. O. Evwaraye ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Hall Effect ◽  
Deep Level ◽  
Polarized Light ◽  
Conduction Band Edge ◽  
Optical Investigation ◽  
Admittance Spectroscopy ◽  
Acceptor Level ◽  
Transient Spectroscopy ◽  
Spectroscopy Optical

AbstractHall effect, deep level transient spectroscopy, optical absorption, and optical admittance spectroscopy were employed to determine the position of the vanadium acceptor and vanadiumnitrogen complex in vanadium- and nitrogen-doped 4H and 6H SiC. Hall effect results indicate that the acceptor position in 4H(6H) SiC is 0.80(0.66) eV beneath the conduction band edge. The DLTS signature of the defect in the 4H polytype showed an ionization energy of 806 meV and a capture cross section of 1.8×10−16 cmr−2 The optical absorption measurements proved that the acceptor level investigated is related to isolated vanadium, and therefore the vanadium acceptor level. Based upon DLTS and SIMS measurements, the maximum solubility of vanadium in SiC was determined to the 3×10−17 crn3. An examination of polarized light experiments indicates that vanadium also complexes with another element to form electronic(at 5000 cm−1) and vibrational absorption(at 683 cm−1) bands. While the other constituent cannot be identified, evidence suggests that nitrogen is a likely candidate. This complex introduces a deep level at Ec−0.78 eV as determined using optical admittance spectroscopy.

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