A Precision Measurement of the LII-LIII X-Ray Energy Level Difference in Some Heavy Elements and a Comparison with the Predictions of the Schawlow-Townes Theory of the Nuclear Size Effect

Citation

Shacklett, Robert Lee (1956) A Precision Measurement of the LII-LIII X-Ray Energy Level Difference in Some Heavy Elements and a Comparison with the Predictions of the Schawlow-Townes Theory of the Nuclear Size Effect. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/2YQG-G079. https://resolver.caltech.edu/CaltechETD:etd-06252004-140127

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The recent experimental determinations of the radius of the nuclear charge distribution all tend to give an approximate value of [...] with [...]. However, the theoretical work of Schawlow and Townes on the effect of the finite nuclear size on the [...] X-ray level splitting, through a comparison with already existing X-ray data, yielded a value of [...]. This thesis describes an experimental determination of the [...] splitting for six of the heavy elements based on two-crystal spectrometer measurements of the Bragg angles of the [...] and [...] X-ray lines of W, Pt, Bi, Th, U, and Pu. The Bragg angles of these lines, corrected for vertical divergence, temperature, and crystal diffraction pattern asymmetry, are reported with a mean standard deviation of about 0.2 second of arc. The values of the [...] splitting calculated from the wavelengths of the lines have a relative accuracy of about 50 parts per million. When the experimental splittings are compared to the theoretical values which include the nuclear size effect, a value of [...] is obtained. The suggestion is made that inaccuracies in the previous measurements of the [...] wavelengths for several high Z elements might have contributed to the large value of [...] obtained by Schawlow and Townes. When the theoretical splitting is calculated with corrections for vacuum polarization and a nuclear radius constant of [...], a comparison with experiment shows that a discrepancy remains which is then used to evaluate an empirical correction term. The sign, magnitude, and Z-dependence of this term suggest that the remaining discrepancy might arise from the Lamb shift effect.

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