REARRANGEMENT COLLISIONS WITH POLARIZED POSITRON BEAMS AND MOLECULAR-OXYGEN TARGETS

Angular-momentum coupling and density-matrix techniques are used to st udy the formation of para- and orthopositronium in rearrangement colli sions involving a slow polarized positron beam and a molecular oxygen target. Spin scattering matrices are obtained by ensuring spin conserv ation in the interaction region, and spin density matrices for the inc oming positron-oxygen system are constructed to include an angular dep endence between the spin-quantization axes of the two incoming beams. The ratios of para- to ortho-positronium formation are given for the s cattering process O-2 + e(+) --> O-2(+) + Ps for an unpolarized as wel l as a polarized oxygen target. The variation from the statistical Val ue of 1/3 is predicted in both cases. Experimental verification should be possible with modest upgrading of existing positron beam facilitie s.