Aftereffects of Auger Ionization Following Electron Capture in Cobalt Complexes
Several cobalt complexes labeled with Co57 were studied. In complexes, where cobalt is held in a large and highly conjugated ring system, it is shown that the bonds escape fragmentation after the Auger event. On the other hand, in some complexes with nonconjugated structures, there is evidence for complete fragmentation. In the intermediate category of complexes, there exists a certain probability for the molecule to escape fragmentation. Attempts have been made to distinguish between the two possibilities—failure to fragment versus fragmentation followed by reentry of57Fen+ into a neighboring molecule through excited exchange within 10-7 sec. This has been done by investigating the spectra of labeled complexes diluted in inert matrices and inactive cobalt complexes doped with 57Co++.
The absence of fragmentation in highly conjugated ring systems opens up interesting possibilities for the use of Mössbauer emission spectroscopy for systematic study of Vitamin B12, its analogs, and other biologically important molecules possessing conjugated ring systems, for instance, porphyrins. It can also find applications in the study of bulky iron-bearing molecules where iron can be replaced by cobalt; in such cases, the emission Mössbauer spectroscopy would be decidedly more sensitive than the conventional absorption Mössbauer spectroscopy.
KeywordsCobalt Complex Outer Line Auger Event Excited Exchange Quadrupolar Split Doublet
Unable to display preview. Download preview PDF.
- 2.S. Wexler, in: Actions Chemiques et Biologiques des Radiations, M. Haissinsky, ed. (Masson, Paris, 1965), Vol. 8, pp. 103–241.Google Scholar
- 3.A. H. Snell, α, ß, and γ-Spectroscopy, K. Siegbahn, ed. (Interscience, New York, 1964), p. 1545.Google Scholar
- 11.G. M. Bancroft, A. G. Maddock, W. K. Ong, R. H. Prince, and A. J. Stone, J. Chem. Soc. A, p. 1966 (1967).Google Scholar
- 13.J. Shankar, Amar Nath, and M. H. Rao, Radiochim. Acta 3:26 (1964).Google Scholar
- 14.Amar Nath, S. Khorana, P. K. Mathur, and S. Sarup, Indian J. Chem. 4:51 (1960).Google Scholar
- 17.R. H. Herber and H. A. Stöckler, in: Proceedings of the Symposium on Chemical Effects of Nuclear Transformations, I.A.E.A., Vienna (1965), Vol. II, p. 403.Google Scholar
- 18.J. L. Thompson, private communication.Google Scholar
- 19.Amar Nath, Melvin P. Klein, and Walter Kündig, unpublished work.Google Scholar