Spin Determination Of Intermediate Structure In Subthreshold Fission Of Np-237

A polarized neutron beam and a polarized target have been used to determine spins of 15 intermediate structure groups observed in the fission of / sup 237/Np below 1 keV and of 94 resonances observed in transmission below 102 eV. The pulsed neutron beam, from the Oak Ridge electron linear accelerator, was polarized by transmission through a dynamically polarized proton sample. The / sup 237/Np, in the ferromagnetic compound NpAl/sub 2/, was cooled by a /sup 3/He-/ sup 4/He dilution refrigerator. Nine individual fine-structure resonances comprising the first group at 40 eV were determined to have the same spin, J = 3, substantiating the current interpretation of intermediate structure in subthreshold fission in terms of the Strutinsky double-humped deformation barrier. Correlation of these results with existing data on the angular distribution of fission fragments from aligned /sup 237/Np indicates an apparent admixing of transition states, as evidenced by nonintegreal values of the projection quantum number, K. (auth)