Independent cross sections for all the $\mathrm{Hg}$ isotopes produced in the reaction of $600\text{−}\mathrm{MeV}$ ${}^{18}\mathrm{O}$ with a molten natural $\mathrm{Pb}$ target have been measured down to about $2\mu \mathrm{b}$. The measurement is based on a radiochemical gamma-spectroscopy technique combined with rapid gas thermochromatography. The observed $\mathrm{Hg}$-isotope distribution from ${}^{180}\mathrm{Hg}$ to ${}^{209}\mathrm{Hg}$ is compared with those previously reported from the reaction of $600\text{−}\mathrm{MeV}$ $p$ with a natural $\mathrm{Pb}$ target, and from two-proton-removal reactions measured by the inverse-kinematics method at relativistic energies. The comparisons make available some additional information for improving knowledge of spallation-reaction mechanisms in peripheral nuclear collisions. It is noted that the production cross sections for neutron-deficient heavy residues and the yield of fast neutrons emitted in proton-induced reactions should increase with increasing incident proton energy from $600\mathrm{MeV}$ to $1\mathrm{GeV}$.

• Received 12 July 2001

DOI:https://doi.org/10.1103/PhysRevC.70.024603