Activation Cross Sections for (n, 2n) Reactions at 14.4 MeV in the RegionZ=40−60: Precision Measurements and Systematics

Activation cross sections for the ($n, 2n$) reaction in the region of $Z=40-60\mathrm{}$ at 14.4±0.3 MeV have been measured by using the mixed-powder method and Ge(Li) $\gamma$-ray detection. The total cross sections ($m+g$) measured are (in mb) ${\mathrm{Zr}}^{90}$, 652±31; ${\mathrm{Zr}}^{96}$, 1456±80; ${\mathrm{Mo}}^{92}$, 217±18; ${\mathrm{Mo}}^{100}$, 1389±84; ${\mathrm{Ru}}^{96}$, 569±30; ${\mathrm{Ru}}^{98}$, 1168±96; ${\mathrm{Ru}}^{104}$, 1440±80; ${\mathrm{Rh}}^{103}$, 957±57; ${\mathrm{Pd}}^{102}$, 637±45; ${\mathrm{Pd}}^{110}$, 1416±150; ${\mathrm{Cd}}^{108}$, 865±100; ${\mathrm{Cd}}^{110}$, 1221±150; ${\mathrm{Cd}}^{116}$, 1389±71; ${\mathrm{Sn}}^{114}$, 1239±130; ${\mathrm{Sb}}^{121}$, 1615±63; ${\mathrm{Sb}}^{123}$, 1542±80; ${\mathrm{Te}}^{122}$, 1615±110; ${\mathrm{Te}}^{128}$, 1661±161; ${\mathrm{Te}}^{130}$, 1455±55; ${\mathrm{I}}^{127}$, 1649±80; ${\mathrm{Cs}}^{133}$, 1542±75; ${\mathrm{Ba}}^{132}$, 1574±100; ${\mathrm{Ce}}^{136}$, 1318±90; ${\mathrm{Ce}}^{140}$, 1593±130; and ${\mathrm{Ce}}^{141}$, 1730±170. Some partial ($n, 2n$) cross sections also are reported. The measured values are compared with the semiempirical predictions of Pearlstein and of Gardner. No significant shell effects are seen, and the data suggest that 14-MeV ($n, 2n$) reactions are governed predominantly by the statistical model of the compound nucleus. An empirical fit for the ratio of neutron emission to all modes of compound-nucleus decay,