Evidence of the Participation of Electronic Excited States in the Mechanism of Positronium Formation in Substitutional Tb1-xEux(dpm)3 Solid Solutions Studied by Optical and Positron Annihilation Spectroscopies

2012 ◽  
Vol 733 ◽  
pp. 245-248 ◽  
Author(s):  
Welington F. Magalhães ◽  
Fernando Fulgêncio ◽  
Fernando C. de Oliveira ◽  
Dario Windmöller ◽  
José C. Machado ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Excited States ◽  
Solid Solutions ◽  
Electronic States ◽  
Positronium Formation ◽  
Metal Charge ◽  
Positron Annihilation Lifetime ◽  
Electronic Excited States ◽  
Relevant Role ◽  
Metal Charge Transfer

Positron annihilation lifetime (PALS) and photoluminescence spectroscopies measurements were performed in Tb(III) and Eu(III) dipivaloylmethanates, Tb(dpm)3and Eu(dpm)3, and also on their binary solid solutions of general formula Tb1-xEux(dpm)3. A correlation between the5D4Tb(III) energy level lifetime and the positronium formation probability was observed, indicating that the ligand-to-metal charge transfer LMCT states act in both luminescence quenching and positronium formation inhibition. From these results, a new model is proposed, showing that excited electronic states have a relevant role in the positronium formation mechanism.

scholarly journals Роль состояний переноса заряда "лиганд-металл" в процессах возбуждения люминесценции индолкарбоксилатов европия

2022 ◽  
Vol 130 (1) ◽  
pp. 121
Author(s):  
В.И. Царюк ◽  
К.П. Журавлев
Keyword(s):  
Excitation Energy Transfer ◽  
Electronic States ◽  
Decisive Role ◽  
Low Energy ◽  
Excitation Spectra ◽  
Metal Charge ◽  
Ternary Compounds ◽  
Aromatic Carboxylates ◽  
Metal Charge Transfer

The luminescence excitation energy transfer in europium and terbium indole-3-carboxylates, indole-3-acetates and indole-3-propionates as well as ternary indolecarboxylates containing 1,10-phenanthroline and 2,2'-bipyridine molecules have been studied. The luminescence excitation spectra, the lifetimes of the 5D0 (Eu3+) and 5D4 (Tb3+) states, and the luminescence intensity are analyzed. The decisive role of ligand-metal charge transfer (LMCT) states in the quenching of the luminescence of europium aromatic carboxylates containing a π-excessive pyrrole or indole fragment is demonstrated. Most europium compounds are characterized by quenching due to the depopulation of the 5D0 state of the Eu3+ ion through the low-energy LMCT state. But in some ternary compounds, the LMCT state being of higher energy participates in the nonradiative depopulation of the excited electronic states of the ligand.

Studies of the ionization of molecules by electron impact - II. Excited states of the molecular ions of methane and the methyl halides

1957 ◽  
Vol 241 (1225) ◽  
pp. 194-207 ◽  
Keyword(s):  
Excited States ◽  
Electronic Structures ◽  
Mass Spectra ◽  
Electronic States ◽  
Molecular Ions ◽  
Methyl Halides ◽  
Spin Orbital ◽  
Orbital Interactions ◽  
Electronic Excited States ◽  
First Time

The ionization of methane and the methyl halide molecules by essentially mono-energetic electrons, produced by pulse techniques, has been studied in detail in a mass spectrometer. It has been possible to detect for the first time the production of the molecular ions of these compounds in most of their excited electronic states. In the cases of the ions of methyl bromide and iodide we have been able to resolve the components of the doublets of the ground 2 E states which arise from spin-orbital interactions in these molecular ions. The several ionization potentials of each of the molecules which refer to the formation of the ions in their different electronic excited states have been measured. These new results are of interest in that they enable the molecular-orbital theories of the electronic structures of methane and the methyl halides to be assessed. They also provide support for recent theories of the origin of the ions in the mass spectra of organic compounds. It has been demonstrated that there is a monotonic relationship between the ionization potential of electrons in the [ σα 1 ] bonding orbital localized in the C— X bond of these molecules and the corresponding bond dissociation energy.

scholarly journals Delayed fluorescence from a zirconium(iv) photosensitizer with ligand-to-metal charge-transfer excited states

2020 ◽  
Vol 12 (4) ◽  
pp. 345-352 ◽  
Author(s):  
Yu Zhang ◽  
Tia S. Lee ◽  
Joseph M. Favale ◽  
Dylan C. Leary ◽  
Jeffrey L. Petersen ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Excited States ◽  
Delayed Fluorescence ◽  
Metal Charge ◽  
Metal Charge Transfer
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