Cross Section for Excitation ofPb207mby Inelastic Scattering of Neutrons

Abstract

The cross section for the excitation of the 0.8-sec metastable state of ${\mathrm{Pb}}^{207}$ by inelastic neutron scattering has been measured for neutron energies up to 3.1 Mev. Neutrons were produced by the $\mathrm{Li}(p, n)$ reaction. The lowest neutron energy for which excitation is observed is 1.6 Mev. This is in agreement with the level scheme for ${\mathrm{Pb}}^{207}$ based on other information. For the first 800 kev above threshold, the cross section rises approximately linearly, attaining a value of 75 millibarns at 2.4 Mev. After leveling off, it abruptly increases at 2.75 Mev and has a value of 190 millibarns at 3.1 Mev. It is judged that the absolute values of the cross section are accurate to ±40 percent. The absolute cross section for excitation of the metastable state as a function of neutron energy is calculated by the use of the strong interaction theory of nuclear reactions. The theoretical predictions agree well with the measured curve.