Angular Distribution of Fragments from the Fission of Bismuth by 450-Mev Protons

The angular distributions of three fragments from the 450-Mev proton-induced fission of Bi have been measured by a recoil-catching technique involving radiochemical separation of the fission products. The forward velocity component of the fissioning nucleus was determined relative to the velocity of each fragment. If it is assumed that the motion of the fissioning nucleus is directed along the proton axis, the angular distributions in the system of the fissioning nucleus are found to be of the form $a+b{{cos}^2\theta }^{\prime }$, with values of $\frac{b}{a}$ of 0.10±0.01, 0.115±0.015, and 0.09±0.01 for ${\mathrm{Ga}}^{72,73}$, ${\mathrm{Sr}}^{91,92}$, and ${\mathrm{Cd}}^{115,117}$, respectively. The possibility that the motion of the fissioning nucleus is directed at an angle to the proton axis is discussed.