Reactions forming electronically excited free radicals III: Formation of excited molecular states in the H + NF2 reaction

1981 ◽  
Vol 15 (1) ◽  
pp. 31-35 ◽  
Author(s):  
Chew Toong Cheah ◽  
Michael A.A. Clyne
Keyword(s):  
Free Radicals ◽  
Electronically Excited

From free radicals to electronically excited species

1995 ◽  
Vol 19 (1) ◽  
pp. 103-114 ◽  
Author(s):  
Giuseppe Cilento ◽  
Waldemar Adam
Keyword(s):  
Free Radicals ◽  
Excited Species ◽  
Electronically Excited

scholarly journals Nanocracks upon Fracture of Oligoclase

2021 ◽  
Vol 57 (6) ◽  
pp. 894-899
Author(s):  
V. I. Vettegren ◽  
A. V. Ponomarev ◽  
R. I. Mamalimov ◽  
I. P. Shcherbakov
Keyword(s):  
Free Radicals ◽  
Power Law ◽  
Time Interval ◽  
Electron Traps ◽  
Surface Areas ◽  
Electronically Excited ◽  
Order Of Magnitude ◽  
20 Nm

Abstract—The spectrum of fractoluminescence (FL) upon fracture of the surface of oligoclase is obtained. The analysis of the spectrum has shown that fracture of crystals leads to the formation of electronically excited free radicals ≡Si−O• and Fe3• ions as well as electron traps. FL consisted of a set of the signals with the intensities varying by an order of magnitude. The duration of the signals was ~50 ns and the time interval between them varied from ~0.1 to 1 μs. Each signal contained four maxima associated with the destruction of barriers preventing the motion of dislocations along the sliding planes. These breakthroughs cause the formation of the smallest (“primary”) cracks. All other, larger cracks are formed by the coalescence of the “primary” cracks. The sizes of “primary” cracks range from ~10 to 20 nm and the time of their formation is 16 ns. The distribution of cracks by size (surface areas of crack walls) is power law with the exponent –1.9.

scholarly journals Lyoluminescence Dosimetry of L-Proline Incorporated of Sensitizer Dependence on the Temperature and pH of Solution

2019 ◽  
pp. 2156-2162
Author(s):  
Qahtan Adnan Abdulqader ◽  
Ammar Mohammed Alhasan
Keyword(s):  
Free Radicals ◽  
Amino Acid ◽  
Gamma Rays ◽  
The Self ◽  
Solid Matrix ◽  
Extra Energy ◽  
Excited Species ◽  
Electronically Excited ◽  
The Stability ◽  
Dosimeter Material

To increase the sensitivity of dosimeter, it has to improve the properties that are required to increase its sensitivity. It was proven that the dependence of lyoluminscence (LL) of irradiated amino acid (L-prolin) incorporated with chemiluminscence reagent (luciginine) on the pH and temperature of the solution. LL means the emission of light from dissolved material in a suitable solvent, which is previously exposed to ionizing radiation. When the incorporated phosphor irradiated to gamma rays an electronically excited species are trapped within the solid matrix, this extra energy will be emitted in the form of light (  420-500nm), on dissolving the material in water in this test. The LL intensity increases with increasing pH of the solution. The best reproducible and optimum LL intensity is at (pH=8.5-9) of the solution, However, LL intensity will be decreased when the PH is higher than 12. In this value of pH the stability of free radicals is optimum. The same is found for solvent temperature dependence, the optimum LL intensity is at 45-48 oC. LL intensity will increase up to 70 oC,it was found that the total glow increased because of increasing the self-glow of luciginine , but LL intensity will decrease because of dissociation of phisphore structure.  In addition to the self-glow of the sanitizer will increase too at temperate up to 70 oC , however, that will cause self-glow to the dosimeter material.

scholarly journals Микротрещины в гетерогенном твердом теле (песчанике) при трении

2019 ◽  
Vol 61 (7) ◽  
pp. 1318 ◽  
Author(s):  
В.И. Веттегрень ◽  
А.В. Пономарев ◽  
Р.И. Мамалимов ◽  
И.П. Щербаков
Keyword(s):  
Growth Rate ◽  
Surface Layer ◽  
Free Radicals ◽  
Elastic Wave ◽  
Crystal Lattice ◽  
Wave Velocity ◽  
Elastic Wave Velocity ◽  
Electronically Excited

AbstractThe growth rate and size of microcracks, formed in the surface layer of a heterogeneous natural solid (sandstone) under friction were studied via triboluminescence. It was discovered that destruction of the crystal lattice of plagioclase and quartz, composing sandstones, induces triboluminescence signals. Each s-ignal corresponds to a microcrack, whose surface contains electronically excited free radicals ≡Si–O^– and Fe^3+ ions. The size and growth rate of microcracks were assessed by means of analysis of the rate and duration of the buildup of these signals. The growth rate of microcracks turned out to be less than the elastic wave velocity (~700 m/s) and varied from ∼380 to ∼650 m/s. The size of microcracks varied from ∼4 to ∼7 μm. It was assumed that the variation in the size and growth rate of microcracks were caused by differences in value of the barriers, upon breaking which the microcracks appear.

Photogeneration of Organic Free Radicals in Liquid Solutions

2020 ◽  
Vol 17 ◽  
Author(s):  
Igor V. Khudyakova ◽  
Peter P. Levinb
Keyword(s):  
Free Radicals ◽  
Uv Light ◽  
Light Sources ◽  
Bond Dissociation Energies ◽  
Light Emitting ◽  
Dissociation Energies ◽  
Electronically Excited State ◽  
Liquid Solutions ◽  
Electronically Excited ◽  
Weak Chemical

In this brief review we consider the generation of free radicals by irradiation with UV-light solutions of compounds with weak chemical bonds. Bond dissociation energies (BDE) are compared with the energies of photons. Light sources used in industry and academia are listed. Free radicals can be produced by photodissociation and by bimolecular chemical reactions between the electronically- excited state of a molecule and a quencher. Important examples are presented. A special effort is devoted to light-emitting diodes (LED) which gain a wide application in this century. We cited books on the free radicals and photochemistry as an introduction as well as recent publications dated 2020.

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