ISOMERIC CROSS-SECTION RATIOS AND TOTAL CROSS SECTIONS FOR 74SE(N,2N)73G,MSE, 90ZR(N,2N)89G,MZR AND 92MO(N,2N)91G,MMO

The isomeric ratios and excitation functions were measured for the 74Se(n, 2n)73g, mSe, 90Zr(n, 2n)89g, mZr and 92Mo(n, 2n)91g, mMo reactions in the neutron energy range 12-18 MeV. The results are compared with the statistical model predictions. Calculations were performed with the use of the superconductivity model of nuclear level density for closed shell nuclei. In the case of the 90Zr(n, 2n)89g, mZr and 92Mo(n, 2n)91g, mMo reactions the calculated isomeric ratios show good agreement with experimental data, which is not true, however, for the 74Se(n, 2n)73g, mSe reaction. To obtain agreement between the experimental and theoretical isomeric ratios for the latter reaction some changes in the decay scheme of the 73Se nucleus seem to be necessary. For all the reactions investigated the calculated total cross sections do not agree with the measured ones. The disagreement may be due to the fact that no account was taken of the gamma-neutron competition. © 1969.