Evidence for a second kind of trapped electron in some deuterated aqueous glasses at low temperatures. A pulse radiolysis study

1976 ◽  
Vol 54 (3) ◽  
pp. 367-381 ◽  
Author(s):  
George V. Buxton ◽  
Hugh A. Gillis ◽  
Norman V. Klassen
Keyword(s):  
Absorption Band ◽  
Ethylene Glycol ◽  
Low Temperatures ◽  
High Energy ◽  
No Emission ◽  
Infrared Band ◽  
Visible Absorption ◽  
Trapped Electrons ◽  
Visible Band ◽  
Trapped Electron

Several deuterated aqueous glasses have been pulse-irradiated at 76 K. In addition to the well known visible absorption band of et−, a second intense infrared absorption band, with λmax > 3200 nm, has been found in (a) 50% by volume ethylene glycol, (b) 9.5 M LiCl, and (c) 2.5 and 4 M MgCl2 glasses. Electron scavengers decrease the intensities of both bands, but to different extents. An increase in temperature decreases the intensity of the infrared band, but not that of the visible band. These and other features lead us to conclude that the infrared band is due to shallowly trapped electrons which are distinctly different from trapped electrons which absorb in the visible region.The decay of the infrared band extends over several orders of magnitude in time and, unlike that of the visible band, is independent of wavelength. In the two chloride glasses the decay of the infrared band is accompanied by emission (λmax ≈ 410 nm) and is probably due to a spur reaction between an electron and hydroxyl radical to form excited hydroxide ion. No emission is found in the ethylene glycol glass, but growth of the visible band matches the decay of the infrared band in this case.By comparing the amount of Ag0 produced in an ethylene glycol glass containing Ag+ with the decrease in intensity of the infrared and visible bands, we obtain ε1400 = (5.7 ± 0.8) × 103 M−1 cm−1. From the shape of the infrared band, which is Lorentzian on the high energy side, we estimate λmax ≈ 3600 nm and εmax ≈ 4.9 × 104 M−1 cm−1.

Two types of localized excess electrons in crystalline D2O ice

1977 ◽  
Vol 55 (12) ◽  
pp. 2385-2395 ◽  
Author(s):  
George V. Buxton ◽  
Hugh A. Gillis ◽  
Norman V. Klassen
Keyword(s):  
Absorption Band ◽  
Infrared Absorption ◽  
Low Temperatures ◽  
Total Yield ◽  
Equilibrium Concentration ◽  
Electron Trap ◽  
Decay Kinetics ◽  
Infrared Band ◽  
Visible Absorption ◽  
Perfect Lattice

In a pulse radiolysis study of crystalline D2O ice, an intense infrared absorption band with λmax > 2350 nm has been found at low temperatures, in addition to the well-known visible absorption band of the trapped electron. The infrared band is also attributed to trapped electrons, partly because of its similarity to the electron absorption band found recently in some D2O glasses at low temperatures. The effects of temperature, dose per pulse, accumulated dose, and added NH4F, HF, and ND3 on the yields and decay kinetics of both bands have been investigated. It is concluded that the electron trap giving rise to the visible band is a vacancy which at low temperatures is radiation-produced by a two-step spur process. At temperatures close to the melting point the vacancy-trap probably exists before the radiation pulse at equilibrium concentration. The electron trap which gives rise to the infrared band is thought to be a cavity that occurs naturally in the perfect lattice. For previously unirradiated samples the infrared band decays by a second order process which is remarkably fast [Formula: see text] The decay reaction is probably neutralization by D2O+. Doping with NH4F increases the yield of the infrared absorption and greatly decreases its decay rate. The total yield of localized electrons in irradiated crystalline D2O is higher than has been generally recognized.

Partial deconvolution of the absorption spectrum of trapped electrons in 15 M LiCl aqueous glasses at 77 K

1979 ◽  
Vol 57 (14) ◽  
pp. 1758-1764 ◽  
Author(s):  
Tuan Quoc Nguyen
Keyword(s):  
Absorption Spectrum ◽  
Steady State ◽  
Absorption Band ◽  
Relative Magnitude ◽  
Visible Absorption Spectrum ◽  
Green Band ◽  
Visible Absorption ◽  
Time Resolved ◽  
Composite Nature ◽  
Trapped Electron

Evidence is presented for the composite nature of the solvated (or trapped) electron absorption band in LiCl aqueous glass at 77 K. It is shown that the overall visible absorption spectrum can be deconvoluted into a homogeneously-bleachable 'green' band and a heterogeneously-bleachable 'red' band, whose relative magnitude and absorption band-maxima change with the concentration of electrolyte. From the combined results of time-resolved and steady-state photobleaching experiments, it is concluded that at least two unstable bands are formed during photobleaching (with smaller lifetimes for the band lying further towards the infrared) which then reconverted into the 'green' band with over 40% efficiency.

Octahedral–tetrahedral equilibria in aqueous cobalt(II) solutions at high temperatures

1980 ◽  
Vol 58 (14) ◽  
pp. 1418-1426 ◽  
Author(s):  
Thomas Wilson Swaddle ◽  
Leonard Fabes
Keyword(s):  
Sulfuric Acid ◽  
High Temperature ◽  
Absorption Band ◽  
High Temperatures ◽  
Intensity Ratio ◽  
Hydrogen Sulfate ◽  
Sulfate Ion ◽  
Acidic Media ◽  
Visible Absorption ◽  
Upper Limits

Evidence is presented to indicate that aqueous Co2+ exists as the hexaaquo-ion in equilibrium with minor amounts (upper limits 0.08% at 298 K, 7% at 625 K, at 16–25 MPa) of tetraaquocobalt(II), with ΔH ~ +17 kJ mol−1. The single visible absorption band of the supposed Co(H2O)42+ has maxima at 552 nm and 486 nm in the intensity ratio 2:1. Hydrogen sulfate ion (up to 0.5 M at least) does not complex Co2+(aq) detectably in acidic media, 290–625 K, and sulfuric acid therefore holds promise as a non-complexing strong monobasic acid for high-temperature aqueous studies. In water containing 2.0 M or more Cl−, the tetrahedral form of cobalt(II) is CoCl42−, ΔH for the octahedral → tetrahedral equilibrium being +62 kJ mol−1; forCoBr42−, the corresponding ΔH is +70 kJ mol−1, the greater endothermicity accounting entirely for the lower stability relative to CoCl42−.

scholarly journals Modyfikowanie HTPB (α,ω-dihydroksypolibutadienu) w reakcjach estryfikacji, silanizacji, epoksydacji i uwodornienia

2018 ◽  
pp. 30-45
Author(s):  
Michał Chmielarek ◽  
Paweł Maksimowski ◽  
Tomasz Gołofit ◽  
Katarzyna Cieślak ◽  
Wojciech Pawłowski ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Low Temperatures ◽  
Frost Resistance ◽  
High Energy ◽  
Insulating Materials ◽  
Rocket Propulsion ◽  
Materials Research ◽  
Selection Of

HTPB is a valuable comonomer for the preparation of polyurethanes. Thanks to its specific properties, it gives these materials frost resistance and excellent mechanical properties, especially at low temperatures. The polyurethanes thus obtained are used in the production of propellants used in space and military rocket propulsion, and are the basis for frost-resistant adhesives and insulating materials. Research on the selection of binder indicates the use of high energy polymers or modifications of previously used polymers improving their properties. The results of research on ways of changing the properties of HTPB through its modification and thus an increase of application possibilities will be presented.

Synthesis of Fluorescent Magnetic and Plasmonic-Hybrid Multifunctional Nanopaticles

2014 ◽  
Vol 1081 ◽  
pp. 161-164
Author(s):  
Xue Mei Li ◽  
Zheng Guan ◽  
Hong Ling Liu ◽  
Jun Hua Wu ◽  
Xian Hong Wang ◽  
...  
Keyword(s):  
Ethylene Glycol ◽  
Zno Nanoparticles ◽  
Poly Ethylene Glycol ◽  
Visible Absorption ◽  
Transmission Electron ◽  
Good Magnetic Property ◽  
Uv Visible ◽  
Poly Ethylene ◽  
Poly Propylene

FeAu/ZnO nanoparticles were successfully synthesized by nanoemulsion process with the use of poly (ethylene glycol)-block-poly (propylene glycol)-block-poly (ethylene glycol) as the surfactant. The characterization of the FeAu/ZnO nanoparticles was performed using X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV-visible absorption spectroscopy, showing that the polymer-laced nanoparticles reveal high crystallinity, excellent dispersibility and well defined optical performance. The process of solvent dispersion-collection of FeAu/ZnO nanoparticles indicates that the nanoparticles possess good magnetic property for applications.

Synthesis and Properties of 1-[2-trifluoromethylpheny-2-[2-methyl-5-(3,5-difluorophenyl)-3-thienyl] perfluorocyclopentene

2013 ◽  
Vol 468 ◽  
pp. 75-78
Author(s):  
Guang Ming Liao ◽  
Shou Zhi Pu ◽  
Zhi Yuan Sun
Keyword(s):  
Absorption Band ◽  
Fluorescence Intensity ◽  
Emission Intensity ◽  
Uv Light ◽  
Fluorescent Properties ◽  
Visible Absorption ◽  
Photostationary State ◽  
Closed Ring ◽  
Open Ring

An asymmetrical photochromic diarylethene 1-[2-trifluoromethylpheny-2-[2-methyl-5-(3,5-difluorophenyl)-3-thienyperfluorocyclopentene (1o) was synthesized and its phtochromic, fluorescent properties in both solution and PMMA films were investigated in detail. This compound exhibited remarkable photochromism, upon irradiation with 297 nm UV light, the colorless solution of 1o turned to plum with a new visible absorption band centered at 544 nm (ε =3.75 × 103 L mol-1 cm-1) attributable to the closed-ring isomer 1c.The fluorescence intensity of diarylethene decreased dramatically along with the photochromism from open-ring isomer to closed-ring isomer in PMMA films and in hexane. The emission intensity of diarylethene 1o in a photostationary state was quenched to ca. 64% in hexane and 27% in PMMA films.

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