ISOTOPE EFFECTS IN URANIUM-L X-RAY-EMISSION SPECTRA

The isotope shifts of the most intensive UL X-ray emission lines (alph a(2), alpha(1), beta(2), beta(4), beta(5), beta(3), beta(1), gamma(1), gamma(2), gamma(3), and gamma(6)) in the spectra of Cs[UO2(NO3)(3)] w ere accurately measured. The samples of Cs[UO2(NO3)(3)] with the isoto pe compositions (1) U-238 99.25%, (2) U-238 63.5% + U-235 36.5%, (3) U -238 33.5% + U-235 66.5%, and (4) U-235 99.99% were prepared and studi ed spectroscopically. The shifts of the lines beta(4), beta(3), gamma( 2), gamma(3), beta(1), and gamma(6) which are due to the inner electro nic states (2s(1/2) or 2p(1/2)) and directly contribute to the electro n density at the nucleus, reach +20...+270 meV. On the other lines (al pha(2), alpha(1), beta(2), and beta(5)), the effects are considerably lower and have the negative sign. These results qualitatively agree wi th the theoretical predictions of the ''volume'' isotope effect in all X-ray transitions. No appreciable changes in line profiles were obser ved within the errors of the analysis.