X-ray interferometry: the optical to gamma ray connection

Testing of theoretical estimates of the 'optical' transitions of the bound negative muon (muonic x-ray spectra) and K emission spectra of mid- to high- Z atoms is of particular interest. Problems arising in such determinations from measurement imprecision and from the larger inaccuracies in the γ ray reference lines are discussed. A brief schematic description of the four steps forming a simplified connecting chain from the hydrogen Balmer α to a typical γ-ray line is given followed by an inventory of measurements of such γ lines made by the author to date and the results from several recent closure tests in 169Yb. As examples of applications, data are presented both from recent muonic x-ray spectroscopy and also from some high- and mid- Z electronic x-rays. Future work at still higher energies is indicated. (UK)