0 degrees polarization transfer in H2(p-vector,n-vector)pp at 54 and 71 MeV.

Results of measurements of the transverse polarization transfer coefficients ${\mathrm{K}}_{\mathrm{y}}^{\mathrm{y}\ensuremath{'}}$(0\ifmmode^\circ\else\textdegree\fi{}) for ${\mathrm{H}}^{2}$(p\ensuremath{\rightarrow},n\ensuremath{\rightarrow})pp at 54 and 71 MeV are presented. The magnitude and energy dependence of this parameter have been determined with sufficient precision (4%) to permit the use of this reaction as a source of nearly monoenergetic polarized neutrons in precise measurements. ${\mathrm{K}}_{\mathrm{y}}^{\mathrm{y}\ensuremath{'}}$(0\ifmmode^\circ\else\textdegree\fi{}) is found to have a significant dependence on excitation energy. The results at low excitation energy are in agreement with calculations in the impulse approximation using the nucleon-nucleon phase shifts obtained from the Bonn or Paris potentials. A substantial difference from the results obtained using the empirical phase shifts is found. Results of measurements of the longitudinal polarization transfer coefficient ${\mathrm{K}}_{\mathrm{z}}^{\mathrm{z}\ensuremath{'}}$(0\ifmmode^\circ\else\textdegree\fi{}) at 54 MeV are also presented.