Isomeric transition internal conversion

Further work on nickelocene and cobaltocene was done by Ross , who synthesized the respective compounds using Ni, Ni and " Co, which decay be E.C., jS and a fully converted isomeric transition, respectively, all producing radioactive cobalt isotopes. The results showed retentions, after sublimation, of 84%, 83% and 80%, respectively. The composition of the unsublimable residue was largely CoCp2, except for the highly converted "Co, where only 30% CoCpj could be detected. This was interpreted as showing that by internal conversion the molecules are totally destroyed, by the same sort of argument as was used by Riedel and Merz . 

Early attempts by Asinger to enlarge the scope of hydroalumination by the use of transition metal catalysts included the conversion of mixtures of isomeric linear alkenes into linear alcohols by hydroalumination with BU3AI or BU2AIH at temperatures as high as 110°C and subsequent oxidation of the formed organoaluminum compounds [12]. Simple transition metal salts were used as catalysts, including tita-nium(IV) and zirconium(IV) chlorides and oxochlorides. The role of the transition metal in these reactions is likely limited to the isomerization of internal alkenes to terminal ones since no catalyst is required for the hydroalumination of a terminal alkene under these reaction conditions. 

Transition, Isomeric—The process by which a nuclide decays to an isomeric nuclide (i.e., one of the same mass number and atomic number) of lower quantum energy. Isomeric transitions (often abbreviated I.T.) proceed by gamma ray and/or internal conversion electron emission. 

A subsequent picosecond electronic absorption spectroscopic study of TPE excited with 266- or 355-nm, 30-ps laser pulses in cyclohexane found what was reported previously. However, in addition to the nonpolar solvent cyclohexane, more polar solvents such as THF, methylene chloride, acetonitrile, and methanol were employed. Importantly, the lifetime of S lp becomes shorter as the polarity is increased this was taken to be evidence of the zwitterionic, polar nature of TPE S lp and the stabilization of S lp relative to what is considered to be a nonpolar Sop, namely, the transition state structure for the thermal cis-trans isomerization. Although perhaps counterinmitive to the role of a solvent in the stabilization of a polar species, the decrease in the S lp lifetime with an increase in solvent polarity is understood in terms of internal conversion from to So, which should increase in rate as the S -So energy gap decreases with increasing solvent polarity. Along with the solvent-dependent hfetime of S lp, it was noted that the TPE 5ip absorption band near 425 nm is located where the two subchromophores— the diphenylmethyl cation and the diphenylmethyl anion—of a zwitterionic 5ip should be expected to absorb hght. A picosecond transient absorption study on TPE in supercritical fluids with cosolvents provided additional evidence for charge separation in 5ip. 

A 64-d isomer of an even Z, and an odd nucleus with A 90 occurs at 105 keV above the ground state. The isomeric state decays 10% by EC and 90% by IT. If the internal conversion coefficient a = 50, what is the y-ray lifetime and the most likely multipolarity of the isomeric transition If this is a magnetic transition and the isomeric state has Jit = j, what is the Jit of the ground state ... 

A process alternative to isomeric transition is called internal conversion (IC). In some cases, the y-energy is absorbed by a K-shell (inner) electron. This electron is ejected out with lower energy. This ejected electron is the internal conversion electron, and the process is called internal conversion. Some diagnostic and therapeutic radionuclides with corresponding half lives are given below. 

The nuclide Mo decays with a probability of 87 % to " Tc, which decays almost quantitatively by isomeric transition with a half-life of 6 h under emission of 140 keV photons to the ground state Tc. The loss of photons due to internal conversion is reported to be about 10 % [16]. Only 4 10 - % of the decays of " Tc leads under /I -emission directly to stable Ru. 

IT is an abbreviation for isomeric transition. The decay of Ba proceeds both by emission of a 0.66 MeV y-ray and by the conq>etitive process of internal conversion. The ratio between the number of conversion electrons and the number of y-rays emitted in this competition is called the conversion co cient. The amount of internal conversion is not indicated in simplified decay schemes like Figure 4.5. 

The conversion of the allylic enantioface is most likely to proceed via the tx riHCO-octadienediyl-Ni" transition state TSefc[2] (Fig. 5). In accordance with evidence provided from both experimental [17,18] and theoretical [19] studies, allylic isomerization is most Ukely to occur via the ix, ri (C )-octa-dienediyl-Ni" transition state TSiso[3], which constitutes the internal rotation of the vinyl group around the formal C -C single bond (Fig. 5). The explicit investigation of monomer-assisted reaction paths revealed that additional ethylene or butadiene does not accelerate either allyhc isomerization or enantioface conversion by coordinative stabilization of the corresponding transition state. 

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