Recoil Studies of Heavy Element Nuclear Reactions. II

Angular distributions and ranges of recoils from the reactions ${\mathrm{Bi}}^{209}(\alpha , 2n){\mathrm{At}}^{211}$ and ${\mathrm{Cm}}^{244}(\alpha , 2n){\mathrm{Cf}}^{246}$ have been measured. At helium ion energies higher than about 10 Mev above the $Q$ values of these reactions, the results are consistent with a reaction mechanism involving the emission of one or both neutrons in the forward hemisphere.