Isotope enrichment / separation

The phenomenon of multiphoton dissociation finds a possible application in the separation of isotopes. For this purpose it is not only the high power of the laser that is important but the fact that it is highly monochromatic. This latter property makes it possible, in favourable circumstances, for the laser radiation to be absorbed selectively by a single isotopic molecular species. This species is then selectively dissociated resulting in isotopic enrichment both in the dissociation products and in the undissociated material. 

Cu/ Zn0/Si02 catalyst reduced at 700 K [3.147]. These LEIS spectra were obtained at three different ion doses - 3 x 3.41 x 10 and 8.67 x 10 Ne" cm . Because of the use of isotopically enriched Cu and Zn, and of Ne" ions as projectiles, Cu and Zn can clearly be separated in the LEIS spectrum. Strong dose-dependence is apparent. Eig. 3.60b shows the dose-dependent surface concentrations of Cu and Zn. At low doses (<1.5 x lO " Ne cm ) the Zn concentration remains constant whereas the Cu concentration increases. At these low doses a hydroxyl layer on top of the catalyst is sputtered. The Zn signal stays constant despite removal of the adsorbate, indicating that at the virgin surface the Zn concentration was even higher. 

The isotopically enriched carbonyl can be separated from the CO and SF6 in a circulating vacuum system.]... 

In the analysis of seawater, isotope dilution mass spectrometry offers a more accurate and precise determination than is potentially available with other conventional techniques such as flameless AAS or ASV. Instead of using external standards measured in separate experiments, an internal standard, which is an isotopically enriched form of the same element, is added to the sample. Hence, only a ratio of the spike to the common element need be measured. The quantitative recovery necessary for the flameless atomic absorption and ASV techniques is not critical to the isotope dilution approach. This factor can become quite variable in the extraction of trace metals from the salt-laden matrix of seawater. Yield may be isotopically determined by the same experiment or by the addition of a second isotopic spike after the extraction has been completed. 

The primed or unprimed symbols refer to isotope fractions. The single stage separation factor for infinitesimal product removal (yi/zj 0), (rj)0, is given the symbol a . The i s index the stage number. Most often a is close to unity and it is convenient to define the isotope enrichment factor (the single stage enrichment factor), e, between the i th and (i + l) th stage... 

The extraction of deuterium from natural water feed forms an excellent case study of the application of large scale distillation and exchange distillation to isotope separation. The principal historical demand for deuterium has been as heavy water, D20, for use in certain nuclear reactors. Deuterium is an excellent neutron moderator, and more importantly, it has a low absorption cross section for slow neutrons. Therefore a reactor moderated and cooled with D20 can be fueled with natural uranium thus avoiding the problems of uranium isotope enrichment. This was the... 

A major topic in isotope mass spectrometry is the determination of the half-lives of long-lived radionuclides. De Bievre and Verbruggen34 determined the half-life of 241 Pu for 3-decay in the isobaric radionuclide 241 Am on material from Oak Ridge that had initially been about 93% isotopically enriched. Due to the isobaric interference of 241 Pu and 241 Am radionuclides during mass spectrometric measurements by TIMS, Am had to be removed by chemical separation immediately (less than 48 h) prior to measurements as described in reference 34. On the basis of all the measurements performed over an extended period of more than 20 years and after considering the possible effects of systematic errors during these measurements, a half-life for the 3 decay of 241 Pu of (ti/2 = 14.290 0.006 a) was reported.34... 

Typical results for the overall isotopic separation for Linde X exchanged essentially completely with praseodymium are shown in Table I. Generally, 50-60% of the neutron capture product, 142Pr, was eluted from the zeolite, along with about 1% of the unreacted 141Pr target. In most cases, the isotopic enrichment factor (the ratio of specific activity of metal in the eluate to the average specific activity of all the metal) was in the... 

The 7 Lu target is unique because this material has an extremely low natural isotopic abundance (2.61Z). A sample of several tens of milligrams of LU2O3 was obtained from J he Oak Ridge National Laboratory and had an isotopic enrichment of 70Z in i/8Lu. An additional isotope separation step was done on this sample at LLNL By this procedure we were able to make a target of isotopically pure 176Lu ( 99.9Z) that had a thickness of 22 mg/cm2 and which was supported on a Th substrate. This target was subsequently used for i80 Coulomb-excitation experiments. 

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