Eu and Yb Excitation Mechanisms in ZnS, CaS, SrS and InP

1993 ◽  
Vol 301 ◽  
Author(s):  
M. Godlewski ◽  
K. Światek ◽  
B. Monemar
Keyword(s):  
Energy Transfer ◽  
Rare Earth ◽  
Excited State ◽  
Exciton State ◽  
Experimental Results ◽  
Excitation Mechanism ◽  
Core State ◽  
Excitonic State ◽  
Excitation Mechanisms

ABSTRACTThe role of the excitonic excitation mechanism of the rare earth (RE) intra-shell emission is discussed. Two cases are analyzed. For Yb ion in InP 4f-4f emission of Yb3+ is induced by energy transfer from bound exciton state to the RE core state. For Eu in CaS and SrS RE emission is induced by carrier trapping directly to the excited state of Eu2+ ion. Also in this case the intermediate excitonic state may participate in RE excitation, as suggested by some experimental results.

Vibration suppression and energy transfer by parametric excitation in drive systems

2012 ◽  
Vol 226 (8) ◽  
pp. 2000-2014 ◽  
Author(s):  
Horst Ecker ◽  
Thomas Pumhössel
Keyword(s):  
Energy Transfer ◽  
Parametric Excitation ◽  
Vibration Suppression ◽  
Negative Impact ◽  
Energy Transfer Mechanism ◽  
Engineering Systems ◽  
Excitation Mechanism ◽  
Electrical Drive ◽  
Excitation Mechanisms ◽  
Drive Systems

Drive systems may experience torsional vibrations due to various kinds of excitation mechanisms. In many engineering systems, however, such vibrations may have a negative impact on the performance and must be avoided or reduced to an acceptable level by all means. Self-excited vibrations are especially unwanted, since they may grow rapidly and not only degrade the performance but even damage machinery. In this contribution it is suggested to employ parametric stiffness excitation to suppress self-excited vibrations. In the first part of the article we study the basic energy transfer mechanism that is initiated by parametric excitation, and some general conclusions are drawn. In the second part, a hypothetic drivetrain, consisting of an electrical motor, a drive shaft and working rolls is investigated. A self-excitation mechanism is assumed to destabilize the drive system. Parametric excitation is introduced via the speed control of the electrical drive, and the capability of stabilizing the system by this measure is investigated. It is shown that the damping available in the system can be used much more effectively if parametric stiffness excitation is employed.

Phosphatization Coating-Forming Mechanism Based on Green Phosphating Accelerator Rare Earth Nitrate

2013 ◽  
Vol 838-841 ◽  
pp. 2806-2810
Author(s):  
Juch Kuang
Keyword(s):  
Rare Earth ◽  
Erosion Resistance ◽  
Film Formation ◽  
Substantial Reduction ◽  
Experimental Results ◽  
Forming Mechanism ◽  
Rare Earth Nitrate

Experimental results show that the samples gained in bath added Rare earth nitrate (REN), relative to the sample got in bath without REN, improve the anti-corrosion power of the coating because of increasing of covering rate of formless crystal Zn2Fe(PO4)2·4H2O (marked P) crystals and the ratio of P/(P+H) (H is the mark of Zn3(PO4)2 crystal) in the coating, combination of which with components parsing by EDS indicates that the sequence of contribution elements P and Zn to erosion resistance of coatings is P>Zn. And the correlative mechanism was discussed, which has it clear that RE is materially a catalyst holding excellent ability of carrying oxygen and cathode depolarization, its concentration gets so constant in certain range that it is much steadier and more efficient than the usual consumptive oxidants like nitrates. In a word, REN plays the role of surface regulator, accelerant and densification agent, which speeds up the phosphating, and bids it effective to enhance the anti-corrosion power of the coating. The addition of REN, not only promote the phosphating film formation and substantial reduction or exemption of nitrite. So, REN is green phosphating accelerator of live up to one's name.

scholarly journals Photosensitized, energy transfer-mediated organometallic catalysis through electronically excited nickel(II)

Science ◽  
2017 ◽  
Vol 355 (6323) ◽  
pp. 380-385 ◽  
Author(s):  
Eric R. Welin ◽  
Chip Le ◽  
Daniela M. Arias-Rotondo ◽  
James K. McCusker ◽  
David W. C. MacMillan
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Transition Metal Catalysis ◽  
Organometallic Complexes ◽  
Mechanistic Studies ◽  
Metal Catalysis ◽  
Organometallic Catalysts ◽  
Organometallic Catalysis ◽  
Electronically Excited

Transition metal catalysis has traditionally relied on organometallic complexes that can cycle through a series of ground-state oxidation levels to achieve a series of discrete yet fundamental fragment-coupling steps. The viability of excited-state organometallic catalysis via direct photoexcitation has been demonstrated. Although the utility of triplet sensitization by energy transfer has long been known as a powerful activation mode in organic photochemistry, it is surprising to recognize that photosensitization mechanisms to access excited-state organometallic catalysts have lagged far behind. Here, we demonstrate excited-state organometallic catalysis via such an activation pathway: Energy transfer from an iridium sensitizer produces an excited-state nickel complex that couples aryl halides with carboxylic acids. Detailed mechanistic studies confirm the role of photosensitization via energy transfer.

Site selective fluorescence and purity of a rare earth garnet crystal

1981 ◽  
Vol 59 (16) ◽  
pp. 2441-2448 ◽  
Author(s):  
L. V. Haley ◽  
B. Jacquier ◽  
J. A. Koningstein
Keyword(s):  
Energy Transfer ◽  
Rare Earth ◽  
Fluorescence Spectroscopy ◽  
Fluorescence Spectrum ◽  
Experimental Results ◽  
Garnet Crystal ◽  
Excitation Spectra ◽  
Site Selective

Site selective fluorescence spectroscopy of a crystal of europium gallium garnet containing Cr3+ as an impurity has been carried out. An analysis of the experimental results reveals that the strongest fluorescence spectrum between 590.0 nm and 620.0 nm is due to emission from an Eu3+−Cr3+ pair. Fluorescences of farther removed pairs and that of Eu3+ occupying the 8-coordinated d site and 6-coordinated Ga3+ site are also assigned. Energy transfer between the various sites occurs while the excitation spectra for the R lines of Cr3+ show that extremely fast transfer takes place between the R2 and R1 levels.

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