AbstractsPhysics

Gamma-gamma directional correlations were measured in Ba¹³⁴ at ten angles between 90 degrees and 180 degrees in ten degree increments using a scintillation spectrometer. The spectrometer which used NaI crystals, differential energy selection, and standard coincidence techniques was tested by measuring the directional correlation of the two cascade gamma rays in Ni⁶⁰ to be in satisfactory agreement with published results and with theoretical predictions. Cs¹³⁴ decays by beta emission to form several excited states below 2 Mev¹³⁴ in Ba¹³⁴ which subsequently decay to the ground state by the emission of gamma rays. Two correlation measurements were performed in Ba¹³⁴. The first, the "overall" correlation, consists of the 797 Kev-605 Kev, 802 Kev-563 Kev, 559 Kev-797 Kev, and the 802 Kev-[563 Kev]-605 Kev correlations. The second, the "separated" correlation, contains the 797 Kev-605 Kev and the 802 Kev-[563 Kev]-605 Kev correlations. The experimental correlation coefficients are consistent with angular momentum assignments of 2, 2, 4, 4 to the 605 Kev, 1168 Kev, 1401 Kev, and 1970 Kev excited states respectively. These states are assumed to have positive parity. An analysis of the data in terms of the electric quadrupole to magnetic dipole mixing ratios of the 569 Kev and the 553 Kev radiations reveals that, within the limits of experimental error, each radiation contains at least a 50 percent magnetic dipole admixture. The other gamma rays involved are assumed to be essentially pure electric quadrupole. This result contradicts the asymmetric rotor model of the nucleus, which, although it accurately predicts the measured energies of the states with these angular momentum and parity assignments in Ba¹³⁴, does not allow magnetic dipole transitions between the rotational states.