Isomeric Transition Decay

In IT decay from a metastable state to its ground state of a nucleus, an internal conversion process often occurs and as a result, characteristic X-ray emissions are observed. The chemical effect of the X-ray intensity ratio was first studied by Yoshihara and 

A and B, respectively. The results for the three types of d ay are shown in Fig. 4. The ratio increases linearly with increasing for each transition, except for metallk  

Conversicm electron spectroscopy of Tc in metallic technetium and ammonium pertechnetate revealed different patterns between them Participation of 0(2s) electrons was consid ed in the latter compound. 

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IT = isomeric transition, EC = electron capture, l3 = positron emission, and j3 = beta decay. 

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 . 

The two Mossbauer levels of Pt, 99 keV and 130 keV, are populated by either EC of Au(fi/2 = 183 days) or isomeric transition of Pt(fi/2 = 4.1 days). Only a few authors, e.g., [323, 324] reported on the use of Pt, which is produced by thermal neutron activation of " Pt via " Pt(n, y) Pt. The source used in the early measurements by Harris et al. [322, 325] was carrier-free Au diffused into platinum metal. Walcher [326] irradiated natural platinum metal with deuterons to obtain the parent nuclide Au by (d, xn) reactions. After the decay of short-lived isotopes, especially Au(fi/2 = 6.18 days), Au was extracted with ethyl acetate, and the Au/Pt source prepared by induction melting. Buym and Grodzins [323] made use of (a, xn) reactions when bombarding natural iridium with... 

Isomers—Nuclides having the same number of neutrons and protons but capable of existing, for a measurable time, in different quantum states with different energies and radioactive properties. Commonly the isomer of higher energy decays to one with lower energy by the process of isomeric transition. 

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. 

De-excitation of 99mTc has specific features. This nuclide decays with a half-life of 6 hours, but its half-life varies slightly according to environmental conditions [30] or chemical states [31,32], Moreover, the emission probabilities of characteristic X-rays just after the isomeric transition 99mTc — "Tc are influenced by environmental factors [33] which result in a change of the K/VKoc X-ray intensity ratio [34],... 

In the determination of cesium, the coal sample and cesium carrier are digested, and the perchlorate separation and ferric hydroxide scavenging precipitation are made as in the procedure for rubidium. Cesium is then separated from the remaining solution by precipitation of cesium bismuth iodide. The final separation is made by precipitation of cesium chloroplatinate, which is counted with a Geiger counter for the 0.66 MeV /T decay of 134Cs (U = 2.1 yr), or counted for the 0.13 MeV y-ray associated with the isomeric transition of 134mCs (t% = 2.9 hr). 

Mo( , y)99Mo(y3 — decay)99i"Tc(isomeric transition)99Tc... 

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 ... 

Nuclear decay processes that are often used to populate Mossbauer isotope excited states are (30) electron capture (electron + proton neutron), / decay (neutron - proton + electron), and isomeric transition (a long half-life nuclear excited state decays to the Mossbauer excited state). In addition, several of the parent nuclides of the heavy isotopes can be populated by a-particle emission. 

So-called after effects from the decay of the mother isotope can give rise to difficult and even incorrect interpretation of the data. This is often the case for electron capture but not for isomeric transitions. 

For certain nuclides, different physical properties (half-lives, mode of decay) are observed. They are due to different energetic states, the ground state and one or more metastable excited states of the same nuclide. These different states are called isomers or nuclear isomers. Because the transition from the metastable excited states to the ground states is forbidden , they have their own half-lives, which vary between some milliseconds and many years. The excited states (isomers) either change to the ground state by emission of a y-ray photon (isomeric transition IT) or transmutation to other nuclides by emission of cc or particles. Metastable excited states (isomers) are characterized by the suffix m behind the mass number A, for instance Co and Co. Sometimes the ground state is indicated by the suffix g. About 400 nuclides are known to exist in metastable states. 

The charge distributions of the ions found after y " decay of Xe and after isomeric transition of Xe are plotted in Fig. 9.9. The rather similar curves found for the ions of Cs and of Cs result mainly from excitation effects. 

Figure 9.9. Charge distribution of the ions a) after decay of Xe b) after isomeric transition of (According to A. H. Snell, F. Pleasonton, T. A. Carlson Proceedings Series, Chemical Effects of Nuclear Transformations, Vol. I. IAEA Vienna 1961, S. 147.)...

Radioactivity (activity) Property of matter exhibiting (radioactive) decay or isomeric transition of atomic nuclei and emission of nuclear radiation [Bq = s ] Radioanalysis Analysis by means of radioactive atoms (radionuclides) Radiocolloids Colloids (i.e. matter in the colloidal state) consisting of the radioactive matter considered (intrinsic colloids) or containing microamounts of radioactive matter (carrier colloids)... 

In each case, the daughter nucleus is commonly left in an excited state and decays to the ground state by emission of y-rays. If there is a significant delay between the two processes, the y-emission is considered a separate event. Decay by y-emission, resulting in no change in Z or N, is called an isomeric transition (e.g., decay of "Tc to Tc). 

I. Isomeric Iransitian (IT). Isomeric transition is a decay process involving neither the emission nor the capture of a panicle. The nucleus simply changes from a higher to a lower energy level by emitting y-rays. Therefore, both mass number and atomic... 

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