Harbottle

Harbottle, G. Neutron Activation Analysis in Archaeological Chemistry. 157,57-92 (1990). 

Isotope effects in neutron-activated ruthenocene were studied by Harbottle and Zahn . Crystalline samples showed a small ( 10%) effect, but a much larger isotope difference was found in benzene solutions. Frozen solutions were found to be similar to the crystalline samples. 

An interesting study of the recoil behaviour of different nuclides in metal carbonyls was made by Harbottle and Zahn . They studied Cr(CO)6 and Mo(CO)g irradiated in various ways so as to produce nuclear reactions in oxygen and carbon, as well as both high and low energy reactions in Cr and Mo. The results can be briefly summarized as in Table 9. 

Note These values have been assembled from Harbottle and Zahn . The reader is urged to compare the original data for further information. All reactions involve high-energy recoil—(p, pn),(p,p2n),(p,pn) or (y,n)—unless otherwise noted. 

Groening and Harbottle have found a similar isotopic difference in Mo(CO)g between Mo and The retention of the latter... 

Information on isochronal annealing of Mo(CO)g has been given recently by Groening and Harbottle The most interesting result in this work was the clearly stepwise nature of the annealing, as is shown in Fig. 6. Curiously, not only the retention values but also the number and positions of the steps show isotropic differences. No clear explanation was offered other than the suggestion that the effect must arise from differences in the decay modes of the two excited nuclides. 

Fig. 7. Isochronal (lOmin) annealing data for neutron-irradiated MofCO), showing the stepwise annealing and the isotope effect (Redrawn from Groening and Harbottle )...

Harbottle, G., Sutin, N. The Szilard-Chalmers Reaction in Solids. Advan. Inorg. Chem. Radiochem. /, 267—314 (1959). 

One further approach, which has not properly been explored, is based upon the axiom of Harbottle s (29) that if an isotopic difference is found, there must have been little reaction subsequent to the initial hot stage. That is, these subsequent reactions are expected to be normal chemical reactions with essentially no isotopic preference, such that any such reaction would tend to wash out possible isotope effects. This problem is worth pursuing further, since some isotopic effects have been observed where subsequent exchange is to be expected. 

The radiochemistry of ruthenocene has been studied by Baumgartner and Reichold (9) and by Harbottle and Zahn (29). It is found that neutron irradiation of crystalline RuCp2 yields about 10% of the radioactive ruthenium as RuCp2- More specifically, an isotopic difference in the radiochemical yield is found Ru, 9.6 0.1% Ru, 10.7 0.2% and Ru, 9.9 0.2% (29). In liquid solution the isotopic effect is much more pronounced, although the yields are lower. This was suggested by Harbottle as a general principle the greatest isotope effects are associated with the lowest yields. While this principle has not yet been substantiated, it seems reasonable since any thermal reactions which may increase the yields would not likely show any isotope effect. 

Dibenzenechromium was studied by Baumgartner et al. 15). They found that the yield of Cr(Ph)2 was 11.8%. [One cannot fail to be struck by the similarity in yields of FeCp2, RuCp2, and Cr(PhH)2, although it may well be merely coincidence.] On heating the irradiated samples to 110°C, they found the yield to increase to 19.4%. It was found that dissolution of the radioactive crystals in benzene yielded no further Cr(PhH)2. This stands in contrast to the above-mentioned results of Zahn and Harbottle which, though not strictly comparable, show Cp to be quite reactive toward ruthenium atoms. Dibenzenechromium was also formed in low yield 14) from neutron irradiation of PhHCr(CO)3, as will be discussed in more detail later. 

Fig. 3. Stepwise thermal annealing effect in MofCO). From Groening and Harbottle (23).

The difficulty in proving the exact nature of prethermal reactions is that they occur too fast for standard solid-state chemical methods. One attractive idea was expressed by Harbottle 29), namely that, if a strong isotope effect is shown, very little subsequent chemical influence can have been felt and the observed species must have been formed by prethermal processes. The supposition here is that isotopic differences come only from differences in the nuclear deexcitation pattern (total energy, y-ray cascades, angular... 

Less clearly recognizable as scavenging, but in principle the same thing, is the evident reaction of glass surfaces with carrier-free species. While this phenomenon has been studied widely in radiochemistry, adsorption on the walls of glass vessels has been more of a nuisance to be avoided. Harbottle... 

Although attempts have been made to study this reaction using ThC as an indicator, the stability of ThC has restricted these investigations. In 1948 the production of 204,206jj enabled more detailed studies to be made by Harbottle and Dodson and by Prestwood and Wahl. In preliminary reports, these authors presented data for the exchange in perchloric - , hydrochloric and nitric s acid media, obtained using separation methods involving precipitation of (a) T1(I) as chromate or bromide and (b) Tl(IlI) as hydroxide. A rate law... 

Bieber, A. M., D. W. Brooks, G. Harbottle, and E. V. Sayre (1976), Application of multivariate techniques to analytical data on Aegean ceramics, Archaeometry 18, 59-74. 

Harbottle, G. (1990), Neutron activation analysis in archaelogical chemistry, in Yoshihara, K. (ed.), Chemical Applications of Nuclear Probes, Topics in Current Chemistry, Springer, Berlin, Vol. 157, 57-91. 

Harbottle, G. (1982), Chemical characterization in archaeology, in Ericson, J. E. and T. K. Earle (eds.), Contexts for Prehistoric Exchange, Academic Press, London, pp. 13-51. 

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