Isomer shift principles

T. C. Gibb, Principles of Mossbauer Spectroscopy, Halsted, New York, 1976 R. L. Cohen (Ed.), Applications of Mossbauer Spectroscopy, Academic Press, New York, 1976 P. Gtitlich, R. Link, A. Trautwein, Mossbauer Spectroscopy and Transition Metal Chemistry, Inorganic Chemistry Concepts 3, Springer, Berlin, 1978 G. K. Shenoy, F. E. Wagner (Eds.), Mossbauer Isomer Shifts, North-Holland, Amsterdam, 1978... 

The Mdssbauer effect should in principle provide useful information with respect to the bonding in rare earth complexes (Ofer et al., 1968) since the isomer shift is dependent on the electron density at the nucleus. A large number of rare earth nuclei are suitable for Mdssbauer spectroscopy, but only for Eu have complexes been extensively studied. Although a number of early papers appeared, the results were based on the report that the isomer shift in EujO relative to EuFj was less than 0.05 mm s whereas recent investigations have shown that for commercial EU2O3 the Eu isomer shift relative to EuFj-2H20 is... 

Aqueous acidic solutions of either stilbazolium cation exhibit only "monomer" absorption and fluorescence at concentrations of 0.005M or lower. Increasing the stilbazolium concentration in aqueous HCI (0.1-1.0M) to 0.01 M or higher results in a red-shifted, broadened and structureless "excimer" fluorescence and a slightly broadened absorption spectrum (Table 1). Irradiation of these concentrated stilbazolium solutions result in a decrease in the trans- cis isomerization and the formation of the a dimer as the principle photoproduct for both cations (Tables 2 and 3). Although both the cis isomer and the a dimer are formed from each cation in the concentrated homogeneous solution, only the 5 dimer forms from cation 1 while the p dimer and small amounts of the e dimer form from cation 2. 

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