Isotope Shifts in X-Ray Spectra

Abstract

In an electronic, as opposed to a muonic, atom an x-ray transition can exhibit an isotope shift for the same reasons that an optical transition can. Compared with optical transitions, the interpretation of shifts in x-ray transitions is simpler but unfortunately their measurement with precision is not. In practice, the only x-ray transitions in which shifts can be usefully measured are the K lines, and the one invariably studied is the Kα₁ line (1s_1/2-2p_3/2). The theoretical interpretation is simpler than that of optical transitions because only closed shell or single hole configurations are involved. The variation from element to element is smooth and gradual; each element and each stage of ionization is not completely different as in optical spectra.