Absolute Measurements of Internal Conversion Coefficients

Citation

Mills, William Raymond (1955) Absolute Measurements of Internal Conversion Coefficients. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/E32D-W195. https://resolver.caltech.edu/CaltechETD:etd-01262004-103546

Abstract

NOTE: text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. A magnetic lens spectrometer has been used to measure electron yields from the internal conversion of certain nuclear gamma rays. Auxiliary experiments have been performed to determine the effective solid angle of the spectrometer. A technique which has previously proven to be successful has been tested and employed in the measurement of gamma-ray yields by means of a scintillation counter. The combination of conversion electron and gamma yield measurements constitutes an experimental determination of an internal conversion coefficient, and by comparison with theory it is possible to make gamma-ray multipole order assignments. Bi207 decays to an isomeric state of Pb207 at 1.63 Mev which emits two successive gamma rays with energies 1.06 and 0.57 Mev, the decay proceeding through a level at 0.57 Mev. Internal conversion lines from both transitions have been observed previously. We have measured the conversion coefficients and found the 1.06-Mev line to be M4 with E2 indicated for the 0.57-Mev line. Using the reaction [...] we have observed internal conversion lines from the decay of the first two excited states of F19. The transition energies are 109.1 ? 1.0 and 196.8 ? 1.5 kev as determined from the conversion lines. The experimental internal conversion coefficients indicate the following multipole order assignments, in agreement with other data: 109 kev, E1; 197 kev, E2. The first excited state of Na23 at 440 kev has been produced in [...]. We have measured the conversion coefficient of the 440-kev transition and assign it either E1 or M1, the experimental uncertainties preventing a definite assignment. Results of other work are cited which indicate M1 is correct. We have attempted to measure the conversion coefficient of the 470-kev line in Na24 produced in [...]. The low intensity of the line, however, permits only the statement that it is of multipole order less than [...]. The lens spectrometer has also been employed to survey the low energy gamma ray spectrum resulting from [...] and [...]. The electron spectra from external photoelectric converters suggest lines at 118 ? 5 and 275 ? 15 kev from the first reaction and 196.5 ? 4 kev from the latter.

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