scholarly journals Temperature Dependence of the Exciton-Exciton Annihilation Rate Constant in Poly (Di-N-Hexylsilane)

1993 ◽  
Vol 328 ◽  
Author(s):  
R. G. Kepler ◽  
Z. G. Soos
Keyword(s):  
Energy Transfer ◽  
Rate Constant ◽  
Room Temperature ◽  
Polymer Chains ◽  
Annihilation Rate ◽  
Excited State Lifetime ◽  
Fluorescence Depolarization ◽  
Solid Films ◽  
Exciton Annihilation ◽  
Short Time

ABSTRACTFluorescence depolarization studies of polysilane chains in solution have shown that energy transfer along the polymer chains occurs for only a very short time relative to the excited state lifetime and only over short distances before the excited states become trapped in long, low-energy segments. However, in solid films we have shown in previous work that excitons are highly Mobile throughout their 600 ps lifetime at room temperature, presumably because energy transfer among neighboring, parallel chain segments becomes possible. In this paper we report that the exciton-exciton annihilation rate constant decreases by only a factor of five between room temperature and 12 K, showing that the excitons do not become trapped even at low temperatures.

Total and Radiative Triplet-Triplet Exciton-Annihilation Rate Constant in Pyrene Crystals

1973 ◽  
Vol 8 (12) ◽  
pp. 6038-6042 ◽  
Author(s):  
V. Ern ◽  
H. Bouchriha ◽  
M. Bisceglia ◽  
S. Arnold ◽  
M. Schott
Keyword(s):  
Rate Constant ◽  
Triplet Exciton ◽  
Annihilation Rate ◽  
Exciton Annihilation

Exciton fission and annihilation in crystalline tetracene

1977 ◽  
Vol 30 (11) ◽  
pp. 2353 ◽  
Author(s):  
GR Fleming ◽  
DP Millar ◽  
GC Morris ◽  
JM Morris ◽  
GW Robinson
Keyword(s):  
Room Temperature ◽  
Streak Camera ◽  
Annihilation Rate ◽  
Time Resolved Fluorescence ◽  
Time Resolved ◽  
Singlet Exciton ◽  
Exciton Lifetime ◽  
Upper Limit ◽  
Exciton Annihilation ◽  
Hopping Model

The time-resolved fluorescence of tetracene crystals excited by a single 7-ps pulse of 530-nm light has been measured with a streak camera/OMA system. The singlet exciton lifetime was found to be 300�30 ps at 293 K. Singlet-singlet exciton annihilation was observed, and the rate constant found to be 5 x 10-9 cm3 s-1. In order to fit the observed decay curves, an upper limit of c. 1 x 10-9 cm3 s-1 must be set on the singlet-triplet exciton annihilation rate. The measured singlet-singlet exciton annihilation rate is consistent with a hopping model for singlet exciton motion at room temperature.

Room temperature phosphorimetric determination of bromate in flour based on energy transfer

Talanta ◽  
2013 ◽  
Vol 116 ◽  
pp. 231-236 ◽  
Author(s):  
Mario Menendez-Miranda ◽  
Maria T. Fernandez-Argüelles ◽  
Jose M. Costa-Fernandez ◽  
Rosario Pereiro ◽  
Alfredo Sanz-Medel
Keyword(s):  
Energy Transfer ◽  
Room Temperature

Electron‐attachment rate constant for Cl2at room temperature and 250 °C

1979 ◽  
Vol 34 (3) ◽  
pp. 187-189 ◽  
Author(s):  
M. Rokni ◽  
J. H. Jacob ◽  
J. A. Mangano
Keyword(s):  
Rate Constant ◽  
Room Temperature ◽  
Electron Attachment ◽  
Attachment Rate

Room temperature phosphorimetric determination of cyanide based on triplet state energy transfer

2003 ◽  
Vol 491 (1) ◽  
pp. 27-35 ◽  
Author(s):  
Marı́a Teresa Fernández-Argüelles ◽  
José M Costa-Fernández ◽  
Rosario Pereiro ◽  
Alfredo Sanz-Medel
Keyword(s):  
Energy Transfer ◽  
Triplet State ◽  
Room Temperature ◽  
State Energy ◽  
Triplet State Energy

Knoevenagel Condensations Catalyzed by New Oil Shale Recyclable Catalyst at Room Temperature and Assisted by Ultrasounds Irradiations

2021 ◽  
Vol 37 (6) ◽  
pp. 1295-1301
Author(s):  
Elmustapha Ennesyry ◽  
Fathallaah Bazi ◽  
Bahija Mounir ◽  
M’hammed Elkouali Elkouali ◽  
Hassan Hannache ◽  
...  
Keyword(s):  
Heterogeneous Catalyst ◽  
Catalytic System ◽  
Oil Shale ◽  
Room Temperature ◽  
Knoevenagel Condensation ◽  
Recyclable Catalyst ◽  
Short Time

Functionalized alkenes were successfully synthesized via a clean procedure in a short time by using a new recycled heterogeneous catalyst prepared from Moroccan oil shale, this catalyst is characterized by different technics such XRD, BET-BJH, MEB-EDS, and TGA, before it’s has been used in the Knoevenagel condensation between different aldehydes and active methylenes. The results showed that coupling the catalyst with ultrasound irradiations could improve the catalytic system in this transformation by achieving the products in a very short time, the results showed clearly that this catalyst could be considered as excellent recyclable support in Knoevenagel condensation.

Low Temperature Expansion of Polysulfide Rubbers

1966 ◽  
Vol 39 (2) ◽  
pp. 211-216
Author(s):  
B. A. Hunter ◽  
M. J. Kleinfeld
Keyword(s):  
Room Temperature ◽  
Liquid Mixture ◽  
Cumene Hydroperoxide ◽  
Polymer Chains ◽  
Nitrogen Gas ◽  
Blowing Agents ◽  
Disulfide Linkages ◽  
Novel Method ◽  
Rubber Product ◽  
Liquid Polysulfide Rubbers

Abstract A novel method for producing a cellular cured rubber product at room temperature has been developed. Pourable liquid polysulfide polymers are treated with a conventional oxidizing curative and selected water-sensitive or oxidation-sensitive blowing agents. Standing at ambient temperature the viscous liquid mixture gradually “rises” and cures to form a finely porous cellular rubber product. Conventional curatives employed include oxidizing agents such as lead peroxide and cumene hydroperoxide. These convert terminal or pendant thiol groups in the polysulfide polymer chains to chain-connecting disulfide linkages. Water is a byproduct of the curing reaction. In the presence of water-sensitive blowing agents such as, (1) metal salts of azodicarboxylic acid or, (2) metal hydride compounds the water produced in the cure reacts to form copious amounts of nitrogen or of hydrogen. Alternatively, oxidation-sensitive blowing agents such as p, p′-oxybis-(benzene sulfonyl hydrazide) react directly with the oxidizing curative to form nitrogen gas. The blowing reactions are concurrent with cure and efficient and controllable expansion can be achieved. The unique process offers possible economies and special properties in applications of liquid polysulfide rubbers as potting compounds, joint sealants, solvent resistant forms, and cold casting compounds.

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