Proton Strength Functions from (p, n) Cross Sections

To an accuracy of ±10%, ($p, n$) total cross sections averaged over resonances have been measured from threshold to about 500 kev above threshold for 12 nuclei from ${\mathrm{Cl}}^{37}$ to ${\mathrm{Nb}}^{93}$. For each nucleus the excitation function of the average cross section is a monotonically increasing function of proton energy. At 500 kev above threshold the cross sections vary from 40 mb for ${\mathrm{Cl}}^{37}$ to 5×${10}^{-4\mathrm{}}$ mb for ${\mathrm{Nb}}^{93}$. One new threshold, that for ${\mathrm{Se}}^{77}(p, n){\mathrm{Br}}^{77}$, was found to be 2.175±0.004 Mev. In the course of calibrating the neutron detector with an Sb-Be source, a new determination was made of the ${\mathrm{Sb}}^{124}$ half-life: 59.9±0.5 days.