Physics & Astronomy ETDs


John M. Palms

Publication Date



Coulomb excitation studies have been performed on the ytterbium isotopes 171, 172, 173, 174, and 176 using oxygen ions having energies up to 55 MeV. Resulting de-excitation gamma rays have been observed in particle coincidence with a NaI(Tl) detector and as single spectra with a Ge(Li) detector. The ground state rotational bands of the Yb171 and Yb173 isotopes have been excited to the 13/2- level. The 13/2- and 11/2-levels of both nuclei have not been reported before. In addition to the transitions from the ground state band, gamma rays were observed from Yb171 and Yb173 coming from other bands. A search was conducted for transitions from the decay of vibrational states, but none were observed. The gamma rays observed in the various nuclei given in keV are as follows: Yb171 , 67.2, 76.4, 85.0, 109.3, 155.0, 163.9, 170.7, 193.7, 240.0, 256.5, and 262.1; Yb173, 78.3, 100.5, 122.3, 143.7, 178.6, 222.3, 265.7, 272.7, 285.7, and 636.7; Yb172, 78.9, 181.9, 280.1, and 369.0; Yb174, 75.5, 175. 7, 271.9, and 362.7; Yb176, 82.2, 188.9, and 292.2. These transitions all fit well into a level scheme predicted by the pure ro­tational model of Bohr and Mottleson. An examination of this same model was also conducted to determine to what extent the electromagnetic properties of the high angular momentum states of the rotational band of the odd-A nuclei are described by the same set of parameters as the lower states. Assuming that the theoretical values for the E2 transition rates are correct, the Ml transition rates, determined from branching ratios, are found to be in excellent agreement with the theory within the experimental error of about 7 percent. The experimentally determined gK, the gyromagnetic ratio for intrinsic motion, differs from the theoretical value for both Yb171, and Yb173. If one assume that the cause for this is a suppersion of the neutron magnetic moment in these nuclei, an effective gS, the spin gyromagnetic ratio for the neutron, can be calculated to give the experimentally determine value for gK. The gS, eff obtained for Yb171 and Yb173 are very nearly equal to the value of 0.750.

Degree Name


Level of Degree


Department Name

Physics & Astronomy

First Committee Member (Chair)

Christopher Pratt Leavitt

Second Committee Member

H. T. Motz

Third Committee Member

Howard Carnes Bryant



Document Type