Reactions of Hydrated Electron with Various Radicals:  Spin Factor in Diffusion-Controlled Reactions

2007 ◽  
Vol 111 (13) ◽  
pp. 2527-2541 ◽  
Author(s):  
Takatoshi Ichino ◽  
Richard W. Fessenden
Keyword(s):  
Hydrated Electron ◽  
Spin Factor ◽  
Diffusion Controlled

Formation and characterization of transitory platinum–ammonia complex ions using pulse radiolysis

1981 ◽  
Vol 59 (24) ◽  
pp. 3319-3325 ◽  
Author(s):  
Hasan M. Khan ◽  
William L. Waltz ◽  
Robert J. Woods ◽  
Jochen Lilie
Keyword(s):  
Hydrogen Atom ◽  
Pulse Radiolysis ◽  
Aqueous Media ◽  
Hydrated Electron ◽  
Complex Ions ◽  
Initial Product ◽  
Detection Analysis ◽  
Diffusion Controlled ◽  
Ammonia Complex ◽  
Long Term Behavior

The reactions of tetraammineplatinum(II) complex ion with the hydrated electron and hydrogen atom have been investigated in aqueous media using the technique of pulse radiolysis coupled with absorption and conductivity detection. Analysis has also been carried on pulse-irradiated solutions for the formation of free ammonia and for changes in concentration of Pt(II). The hydrated electron and hydrogen atom react with the complex at near diffusion-controlled rates, with the respective rate constant being 1.9 ± 0.1 × 1010 M−1 s−1 and 2.8 ± 0.3 × 1010 M−1 s−1. The nascent products of these reactions are shown to be different transitory species. For the electron reaction, the initial product is Pt(NH3)4+ in which the metal center is formally Pt(I). In acidic media, there is a subsequent and rapid release of two ammonia ligands, with only the second step being measurable (k = 4.2 ± 1.7 × 104 s−1). In the reaction of H atom, the results support the occurrence of an addition process, giving rise to a hydrido type product. This species undergoes a first-order reaction (k = 2.2 ± 0.6 × 104 s−1); however the process is not associated with a change in conductivity, and thus it is not one involving loss of ammonia. Subsequent to this process, the loss of one ammonia ligand is observed, with k = 2.0 ± 0.6 × 103 s−1. The natures of these transients and the long term behavior of these systems are discussed.

A TEM investigation of a hyper-eutectic lead-tin alloy

1988 ◽  
Vol 46 ◽  
pp. 562-563
Author(s):  
John A. Sutliff
Keyword(s):  
Volume Diffusion ◽  
Eutectic Mixture ◽  
Precipitation Reaction ◽  
Directionally Solidified ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Diffusion Controlled ◽  
Discontinuous Precipitation Reaction ◽  
Controlled Precipitation

Near-eutectic Pb-Sn alloys are important solders used by the electronics industry. In these solders, the eutectic mixture, which solidifies last, is the important microstructural consituent. The orientation relation (OR) between the eutectic phases has previously been determined for directionally solidified (DS) eutectic alloys using x-ray diffraction or electron chanelling techniques. In the present investigation the microstructure of a conventionally cast, hyper-eutectic Pb-Sn alloy was examined by transmission electron microscopy (TEM) and the OR between the eutectic phases was determined by electron diffraction. Precipitates of Sn in Pb were also observed and the OR determined. The same OR was found in both the eutectic and precipitation reacted materials. While the precipitation of Sn in Pb was previously shown to occur by a discontinuous precipitation reaction,3 the present work confirms a recent finding that volume diffusion controlled precipitation can also occur.Samples that are representative of the solder's cast microstructure are difficult to prepare for TEM because the alloy is multiphase and the phases are soft.

Quantitative surface damage studies by H.R.E.M.

1989 ◽  
Vol 47 ◽  
pp. 632-633
Author(s):  
S. R. Singh ◽  
H. J. Fan ◽  
L. D. Marks
Keyword(s):  
Solar Wind ◽  
Quantitative Analysis ◽  
Surface Science ◽  
Surface Damage ◽  
Space Environment ◽  
Oxygen Desorption ◽  
The Past ◽  
Diffusion Controlled ◽  
Original Observation ◽  
Substantial Interest

Since the original observation that the surfaces of materials undergo radiation damage in the electron microscope similar to that observed by more conventional surface science techniques there has been substantial interest in understanding these phenomena in more detail; for a review see. For instance, surface damage in a microscope mimics damage in the space environment due to the solar wind and electron beam lithographic operations.However, purely qualitative experiments that have been done in the past are inadequate. In addition, many experiments performed in conventional microscopes may be inaccurate. What is needed is careful quantitative analysis including comparisons of the behavior in UHV versus that in a conventional microscope. In this paper we will present results of quantitative analysis which clearly demonstrate that the phenomena of importance are diffusion controlled; more detailed presentations of the data have been published elsewhere.As an illustration of the results, Figure 1 shows a plot of the shrinkage of a single, roughly spherical particle of WO3 versus time (dose) driven by oxygen desorption from the surface.

Influence of Formulation Variables and Processing Techniques on Drug Release from Carbopol-971 based Matrix Tablets of Cinnarizine and Nimodipine.

2010 ◽  
Vol 2 (1) ◽  
Author(s):  
Singh K. ◽  
Pandit K. ◽  
Mishra N.
Keyword(s):  
Drug Release ◽  
Release Rate ◽  
Polymer Concentration ◽  
Matrix Tablets ◽  
Wet Granulation ◽  
Weight Variation ◽  
Diffusion Controlled ◽  
The Matrix ◽  
Processing Techniques ◽  
Formulation Variables

The matrix tablets of cinnarizine and nimodipine were prepared with varying ratio of Carbopol- 971P and co-excipients of varying hydrophilicity (i.e. dicalcium phosphate and spray dried lactose) by direct compression and wet granulation using alcoholic mucilage. The prepared tablets were evaluated for weight variation, hardness and friability. The influence of concentration of the matrix forming material and co-excipients on the release rate of the drug was studied. The release rate of Cinnarizine (more soluble drug) from tablets followed diffusion controlled mechanism whereas for nimodipine (less soluble drug), the drug release followed case-II or super case- II transport mechanism based on Korsmeyer- Peppas equation. The results indicated that the drug release from matrix tablets was increases with increase in hydrophilicity of drug and co-excipients. The release of drug also increased with thermal treatment and decreasing polymer concentration.

Radiolysis studies on the corrosion inhibitors 1 -hexyn-3-ol, cinnamonitrile, and 1,3-diethyl-2-thiourea

1995 ◽  
Vol 73 (12) ◽  
pp. 2137-2142 ◽  
Author(s):  
A.J. Elliot ◽  
M.P. Chenier ◽  
D.C. Ouellette
Keyword(s):  
Hydrogen Atom ◽  
Hydroxyl Radical ◽  
Temperature Dependence ◽  
Rate Constant ◽  
Rate Constants ◽  
Corrosion Inhibitors ◽  
Hydrated Electron

In this publication we report: (i) the rate constants for reaction of the hydrated electron with 1-hexyn-3-ol ((8.6 ± 0.3) × 108 dm3 mol−1 s−1 at 18 °C), cinnamonitrile ((2.3 ± 0.2) × 1010 dm3 mol−1 s−1 at 20 °C), and 1,3-diethyl-2-thiourea ((3.5 ± 0.3) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile and diethylthiourea, the temperature dependence up to 200 °C and 150 °C, respectively, is also reported; (ii) the rate constants for the reaction of the hydroxyl radical with 1-hexyn-3-ol ((5.5 ± 0.5) × 109 dm3 mol−1 s−1 at 20 °C), cinnamonitrile ((9.2 ± 0.3) × 109 dm3 mol−1 s−1 at 21 °C), and diethylthiourea ((8.0 ± 0.8) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile, the temperature dependence up to 200 °C is also reported; (iii) the rate constant for the hydrogen atom reacting with 1-hexyn-3-ol ((4.3 ± 0.4) × 109 dm3 mol−1 s−1 at 20 °C). Keywords: radiolysis, corrosion inhibitors, rate constants.

Micellar effects on the reactivity of the hydrated electron with benzene

1970 ◽  
Vol 74 (26) ◽  
pp. 4608-4609 ◽  
Author(s):  
Larry K. Patterson ◽  
Janos H. Fendler
Keyword(s):  
Hydrated Electron ◽  
Micellar Effects
Sign in / Sign up

Export Citation Format

Share Document