Fragment mass and kinetic energy distributions forPu242(sf),Pu241(nth,f), andPu242(γ,f)

Energy correlation measurements were performed for the spontaneous fission of ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$, the thermal-neutron-induced fission of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$, and the photofission of ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$ with 12-, 15-, 20-, and 30- MeV bremsstrahlung. The photofission cross section for ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$ was determined up to 30 MeV. For ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$(sf) the overall kinetic energy distribution is strongly asymmetric and the overall mass distribution has a very high peak yield (9%). Important deviations of the average total kinetic energy release $〈E_k^{*}〉$ and the average light and heavy fragment masses $〈m_L^{*}〉$ and $〈m_H^{*}〉$ from the systematics of Unik et al. are also observed for this fissioning system. These effects can be explained in the framework of the static scission point model by the strong preferential formation of a shell-stabilized scission configuration with the neutron number of the heavy and light fragments in the vicinity of the spherical $N=82\mathrm{}$ neutron shell and the deformed $N=66\mathrm{}$ neutron shell, respectively. A decrease of $〈E_k^{*}〉$ with the average excitation energy $〈E_{\mathrm{exc}}\left(E_e\right)〉$, $\frac{d〈E_k^{*}〉}{d〈E_{\mathrm{exc}}\left(E_e\right)〉}=-0.30\mathrm{}\pm 0.04$, is observed in the photofission of ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$. A study of the energy-mass correlations shows that the mentioned decrease is caused predominantly by a diminution of the shell corrections in the mass region of the spherical $N=82\mathrm{}$ neutron shell. A comparison of the mass and kinetic energy distributions obtained in this work for ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$, with previously reported results for ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$ and ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ and with scission point model calculations, is also included.