Absolute ($n, 2n$) cross sections have been obtained by counting double-pulse events in a 240-gal cadmium-loaded liquid scintillator. The detection efficiency was determined experimentally using a spontaneous fission source and known values of $\overline{\nu }$. Conventional methods were used to measure the absolute neutron flux. Cross sections were measured for C, N, F, V, Fe, Cu, Ag, Ta, Cd, Au, Pb, Bi, D, and Be. The values in barns are: C, 0.006±0.006; N, 0.019±0.010; F, 0.062±0.009; V, 0.66±0.05; Fe, 0.50±0.04; Cu, 0.76±0.06; Ag, 1.73±0.13; Ta, 2.64±0.20; Cd, 1.92±0.14; Au, 2.60±0.20; Pb, 2.74±0.20; Bi, 2.60±0.19; D, 0.20±0.02; Be, 0.54±0.04. The ($n, 2n$) cross sections for the last six elements are, within error, equal to the nonelastic cross sections. Nuclear temperatures were calculated.

• Received 17 March 1958

DOI:https://doi.org/10.1103/PhysRev.111.616