Radiochemical studies

Many recent reports on the radiolysis of organic halogen compounds have involved studies of solid state or very low temperature systems (refs. 745, 781, 787, 858, 867, 906, and the use of pulsed techniques - - - - - - . Studies on species adsorbed on silica gel have also been made. The nature of intermediate species and the mechanism of scavenger action have been discussed by a number of investigators (see, for example, references 749, 906, 974, 981). 

With fluoro-compounds, there has been work on the radiolysis of fluorinated methanes , hexafluoroethane , tetrafluoroethylene - , fluorobenzene , cyclic fluorocarbons , trifluoroiodomethane - - , and perfluorocar-bons . Most studies have involved the use of y-radiation, but Yi-Noo Tang and Rowland have discussed the recoil tritium-excitation of ethyl fluoride (and ethyl chloride), providing evidence for 1,2-HX elimination. 

Radiolysis studies on chloro-compounds have included those on chlorinated methanes - - - , 1,2-dichloroethane , chlorotriphenylmethane - , chloroolefins , benzyl chloride - , a-chlorotoluene , and chloroacetic acids . Recoil tritium reactions with dichloromethane and chloroethane have also been reported. 

In the case of bromo-compounds, studies, mostly with Co y-radiation, have been reported on methyl bromide - , ethyl bromide , 1-bromobutane , other linear bromoalkanes , and bromobenzene . Behaviour under neutron-irradiation has been described for bromobenzenes - and bromobenzoic acids . 

Studies on iodo-compounds, mostly with y-radiation, have been reported for methyl iodide - , ethyl iodide - - , other alkyl iodides , vinyl iodide , and trifluoroiodomethane - - . Reactions in the neutron-irradiation of iodobenzene have also been discussed. 

Decay of °Pb(CH3)4 in the gas and in the liquid phase has been studied under different conditions. Bi(CH3)3 [1, 5] and also Po(CH3)2 [1] are assumed as decay products, and evidence of molecular survival, i.e., failure of bond rupture in the primary p- and internal conversion process was obtained [5, 6] see also [7, 10]. [Bi(CH3)4]+ is presumed to be the initial ionic species of the decay process [9,10]. A very detailed study revealed that at low pressures no Bi(CH3)3 is obtained, the primary ion [Bi(CH3)4]+ disproportionates and gives depositions on the wall however, at higher pressures, production of Bi(CH3)3 becomes the dominant process since the primary ion undergoes many collisions before reaching the wall [10]. A volatile organolead compound was produced in a methane atmosphere by Pb recoiling from 

The preparation of Pb(CH3)4 labelled with radioactive isotopes is summarized in Section 1.1.1.1.1 the application of radioactive decay in labelled Pb(CH3)4 as an indicator method to study physical or chemical behavior such as photolysis [3], ligand exchange [2, 4], or uptake and metabolism [15] is described in the relevant sections. 

Thermal dissociation of Pb(CH3)4 in a stream of an inert gas, like N2 or H2, is employed as a source of methyl radicals [127 to 130]. These radicals or Pb(CH3)4 are used to produce and to separate methyl derivatives of recoil atoms produced by the decay of Ra [130 to 133] or 2 Cf [133]. An analogous procedure was proposed for the fast separation of elements 113 to 117 [203]. Generation of methyl radicals from Pb(CH3)4 in an ionization chamber is described in [134] see also [135]. 

Pb(CH3)4, obtained by appropriate conversion of lead from natural samples, is used for studies of isotopic assay of lead by mass spectral analysis, e.g., also for the determination of the geological age of minerals [144 to 153] see also [154, 155, 156]. 

Pb(CH3)4 vapor has been used to fill Geiger counters [170 to 174], and was suggested for use in liquid ionization chambers [175]. Short-lived transients are generated by pulse radiolysis of Pb(CH3)4 dosed with naphthalene and toluene, which can be employed for time-resolved dosimetry of low-energy X-rays [176]. 

Exchange of lead is observed on heating Pb(C2H5)4 and elemental lead containing °Pb but not when lead compounds are employed [4]. Pb(C2Hs)4 labeled with ° Pb [10] or °Pb 

A search for superheavy elements in Pb(C2Hs)4 irradiated with 24 GeV protons was negative [8]. 

Pb(C2Hs)4 is an outstanding agent to reduce knock in gasoline [2, 622, 623]. Other tetraal-kyllead compounds such as Pb(CH3)4 (see Organolead Compounds 1, 1987, Section 

Numerous papers deal with comparative studies of the antiknock properties of Pb(CH3)4 and Pb(C2Hg)4 as well as (CH3)4 nPb(C2H5)n (n = 1 to 3) and mixtures of these compounds in relation to fuel composition and to operating conditions of engines [58, 339, 369, 372, 

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Radiochemical studies indicate that the pore base is the actual site of formation of aluminium oxide, presumably by transport of aluminium ions across the barrier-layer, although transport of oxygen ions in the opposite direction has been postulated by some authorities. The downward extension of the pore takes place by chemical solution, which may be enhanced by the heating effect of the current and the greater solution rate of the freshly formed oxide, but will also be limited by diffusion. It has been shown that the freshly formed oxide, y -AljOj, is amorphous and becomes slowly converted into a more nearly crystalline modifipation of y-AljO . 

Generally speaking, radiochemical studies with organometallic compounds, as with most other compounds, have been undertaken with one or more of the following objectives ... 

Several radiochemical studies have been reported, such as the analysis of phosphorus and chlorine by fast neutron activation and synthesis by radiochemical methods. ... 

May et al. [45] used radiochemical studies to ascertain the behaviour of methylmercury chloride and mercuric chloride in seawater under different storage conditions. The application of 203Hg unambiguously revealed that the loss of mercury observed upon storage of unacidified seawater samples in polyethylene bottles was due to adsorption and to the diffusion of metallic Hg (Hg°) through the container wall. 

Wigckowski and coworkers [51] have carried out electrochemical and radiochemical studies of Cl adsorption using radioactive C1. By combining radiochemical measurements with CV experiments, the potential dependence of adsorption and surface-bulk exchange processes has been studied. 

Finally the ESR spectrum of Nb(7r-allyl)4/alumina was unaffected by the addition of ethylene gas to the ESR sample tube. It is assumed that polyethylene is produced in this process since polymer can be isolated from larger scale reactions under similar conditions. The accepted mechanism for the ethylene growth reaction postulates a steady-state concentration of a a-bonded transition metal-hydrocarbon species which would be expected to modify the ESR spectrum of the supported complex. A possible explanation for the failure to detect a change in the ESR spectrum may be that only a small number of the niobium sites are active for polymerization. Although further experiments are needed to verify this proposition, it is consistent with IR data and radiochemical studies of similar catalyst systems (41, 42, 43). 

Allen, P. W., G. Ayrey, C. G. Moore and J. Scanlan Radiochemical studies of free-radical vinyl polymerizations. Part II. The polymerization of vinyl monomers in the presence of polyisoprenes use of C14-labeled initiators to determine the mechanism of graft-interpolymer formation. J. Polymer Sci. 36, 55 (1959). 

Reisch J, Fitzek A. Photo and radiochemical studies. V. Decomposition of aqueous amidopyrine solutions under the influence of light and y-rays. Deut Apoth-Ztg 1967 107 1358-1359. 

Results of several radiochemical studies at the experimental study area we installed at Maxey Flats have already been described in detail elsewhere (8-10). The areal distribution of radionuclides in the surface soil throughout the site has been mapped. Groundwater flow patterns near the experimental study area have also been mapped using tritium as a groundwater tracer. 

Sajun, M. S. Radiochemical Study of Actinide Elements, Ph.D. Thesis, Bombay Univ. 1981... 

B. Physical and Radiochemical Studies with Bromine Isotopes. 470... 

A radiochemical study [104] of the element distribution in the 238U+238U reaction at the unilac revealed the expected broad distribution of reaction products. Below uranium, where losses by sequential fission of transfer products are not significant, the observed yields decreased exponentially from Z=92 down to Z= 73. This trend was well reproduced [105] by a theoretical model treating nucleon transfer in the intermediate collision complex as a diffusion process. By extrapolation of the model to Z=70 nuclei about 100 microbam total production cross section resulted, associated with broad distributions of neutron numbers and excitation energies. 

The radiochemical separation process Is very Important In radiochemical studies because it makes possible the removal of many Interfering radiations as well as large amounts of target material. 

S. M. Qaim, Radiochemical Studies of Complex Particle Emission in Low and Intermediate Energy Reactions, Radiochim. Acta 70/71,163 (1995)... 

R. Bock (Ed.), Heavy Ion Collisions, 3 Vols., North-Holland, Amsterdam, 1979-1981 D. A. Bromley (Ed.), Treatise on Heavy Ion Science, Vol. 4, Plenum Press, New York, 1985 R. Bock, G. Herrmaim, G. Siegbert, Schwetionenforschung, Wiss. Buchges., Darmstadt, 1993 J. V. Kratz, Radiochemical Studies of Complex Nuclear Reactions, Radiochim. Acta 70/71, 147 (1995)... 

F. David, Radiochemical Studies of Transplutonium Elements, Pure Appl. Chem. 53, 997 (1981)... 

A wide variety of experimental techniques are used in radiochemical studies a review of this subject is beyond the scope of this chapter. The interested reader should refer to the reviews and textbooks of actinide chemistry listed in the Section 9.06.1.2 above. Some general points, which should be considered in evaluating... 

Radiochemical studies and radiochemical synthesis with °Bi(RaEj... 

Radiochemical studies with Bi and related studies with... 

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