A measurement of the first moment of the range distribution of (n,2n) recoils in Au and Nb

The method of determining the range of energetic atoms in solids by measuring the number of recoil atoms produced by a nuclear reaction and emitted from the surface was applied to 196Au (71 keV) in Au and 92Nb atoms (143 keV) in Nb. The radioactive recoils were produced by a (n,2n) process in bombarding the target foils with 14 MeV neutrons. The number of atoms emitted in forward and in backward direction from the foil determines the corresponding first moments of the range distribution. From this, mean ranges in forward direction of 95 A+-25% for 196Au in Au and 276 A+-16% as well as 530 A+-16% for 92Nb in Nb are obtained. With the help of known reflection coefficients the mean ranges in backward direction can also be calculated. (Auth.)