EXPERIMENTAL EVIDENCE FOR AXIAL VECTOR INTERACTION IN THE DISINTEGRATION OF Pr144

A detailed study of the disintegration scheme of Pr144 has been carried out using lens spectrometers, scintillation spectrometers, and fast coincidence techniques. The 2293 kev β-component (1.3%) studied in coincidence with γ 691 has a predominantly first forbidden unique shape and the β–γ directional correlation is strongly anisotropic. The results indicate a probable spin-sequence 0−(β)2+(γ)0+, but the accuracy is not sufficient to exclude completely a 1− assignment for the Pr144 ground state. The β 803 component (1.0%) observed in coincidence with γ 2181 has an allowed shape and the β–γ directional correlation is isotropic. The shape of the total β-spectrum was studied in a double lens spectrometer having good anti-scattering properties using sources of Ce144 oxide sublimed onto 200 μg/cm2 Al leaf. Subtraction of a unique (Bij) shape 2293 kev 1.3% component and an allowed shape 803 kev 1.0% component yields the ground state β-spectrum. Analyses were made using the electronic functions of Zerianova which assume uniform charge distribution with ρ = 1.2 A1/3 10−13 cm as well as the point charge functions of Rose with ρ = 1.41 A1/3 10−13 cm. The observed spectrum shape can be explained on 0− to 0+ selection rules only by the axial vector interaction. Limits on the permissible tensor or pseudoscalar admixtures with the axial vector are discussed. No acceptable fit is possible with tensor, pseudoscalar, or any TP admixture (interfering or not) using Rose and Osborn's pseudoscalar formalism.