An Investigation of the Ta¹⁸¹ Nucleus

Citation

Muir, Arthur H. (1960) An Investigation of the Ta¹⁸¹ Nucleus. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9RT5-FA08. https://resolver.caltech.edu/CaltechETD:etd-08152006-090808

Abstract

The nuclear levels of Ta181 were investigated by the study of the [beta]-decay of Hf181 and the electron capture decay of W181. The previously reported 476 kev transition from the Hf181 decay was found not to be in coincidence with the 482 kev transition, thus ruling out the level proposed at 958 kev. Evidence for weak M-shell conversion lines of a ~6 kev transition in the Hf181 decay was found with a 180° [beta]-spectrometer. A [beta]-spectrometer investigation of the W181 decay revealed strong M-shell conversion lines which correspond to a transition of 6.25 ± 0.3 kev in energy. On the basis of the above mentioned results and other considerations, it is concluded that the 476 kev transition in the Hf181 decay occurs between the 482 kev level and the new 6 kev level. A 6 kev [gamma]-ray was also found in the W181 decay with an argon proportional counter. From these studies, the conversion coefficient of the 6 kev transition was determined to be [alpha]T = 44 ± 7. The conversion coefficient and the M-subshell conversion ratios require that the 6 kev transition is of El multipolarity. From this assignment and other experimental and theoretical considerations, it is concluded that the 6 kev level is the 9/2 - [514] Nilsson intrinsic state. Arguments can also be made that the previously reported 152 kev transition in the W181 decay occurs between a new 11/2- rotational level at 158 kev and the 6 kev level. From a measurement of the tantalum L/K x-ray intensity ratio, the W181 electron capture L/K branching ratio (to the ground state and the 6 kev level) is found to be PL/PK = 0.359, and the W181 decay energy is found to be 176(+44)(-22) kev. The branchings of this decay to the various Ta181 levels are as follows: 158 kev (0.12%), 136 kev (0.075%), 6.25 kev (~35%), and 0 kev (~65%). All findings and proposals are consistent with the unified model of the nucleus.

Thesis Files