First-chance fission probabilities $\left(P_{f1}\right)$ of various Am, Pu, and Np isotopes are found to display a significant neutron odd-even stagger (OES), and an obvious excitation energy dependence of the OES is presented. Moreover, a prominent dissipation effect on the OES is revealed, and the differences in $P_{f1}$ of two neighboring fissioning isotopes ${}^{231}\mathrm{Am}$ and ${}^{232}\mathrm{Am}$, ${}^{230}\mathrm{Pu}$ and ${}^{231}\mathrm{Pu}$, and ${}^{225}\mathrm{Np}$ and ${}^{226}\mathrm{Np}$, $\mathrm{\Delta }{P}_{f1}$ (which denotes the amplitude of the OES), are shown to be a quick decreasing function of the dissipation strength $\left(\beta \right)$. This means that the amplitude of the OES is a sensitive experimental indicator of nuclear dissipation properties, and it is proposed here as a new experimental signature to constrain $\beta$. Additionally, we find that $P_{f1}$ of ${}^{231,233}\mathrm{Am}$, ${}^{230,232}\mathrm{Pu}$, and ${}^{225,227}\mathrm{Np}$, whose neutron numbers are even, respectively exhibit an apparently greater sensitivity to $\beta$ than that of their neighboring isotopes ${}^{232}\mathrm{Am}$, ${}^{231}\mathrm{Pu}$, and ${}^{226}\mathrm{Np}$, whose neutron numbers are odd. The neutron odd-even effect is shown to be responsible for the marked enhancement in the sensitivity of the former, clearly indicating its strong influence on using $P_{f1}$ to probe $\beta$. These results suggest that on the experimental side, to more stringently constrain nuclear dissipation by measuring first-chance fission probability, it is optimal to produce those heavy fissioning systems with even neutron numbers.

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• Fission
• Low & intermediate energy heavy-ion reactions
• Models & methods for nuclear reactions
• Nuclear binding
• Nuclear reactions
• 190 ≤ A ≤ 219
• A ≥ 220